Verdict up front: choose the CD100 at £185.99 when your household or small office mixes EE with O2, Vodafone or Three across a 100 m² space; it is the only one of the three that amplifies Band 20 at 800 MHz and Band 3 at 1800 MHz together, serving EE 4G plus calls and O2, Vodafone and Three 4G in one box rated for 100 m² and 10 users at ≥10 dBm output, ≥45 dB uplink gain and ≥50 dB downlink gain. Choose the C100 at £109.99 only when every resident is on O2, Vodafone or a Band 20 MVNO and EE never appears, saving £76.00. Choose the D250 at £169.00 only when every device is EE and the property spans up to 250 m², accepting that O2, Vodafone and Three receive nothing.

The CD100 versus C100 gap is £76.00 (185.99 minus 109.99) and buys the entire Band 3 layer: EE 4G LTE data plus 2G voice calls that the C100 cannot produce at any gain setting. The CD100 versus D250 gap is £16.99 (185.99 minus 169.00) and buys the entire Band 20 layer for O2, Vodafone and Three 4G, while accepting the D250's larger 250 m² footprint shrinks to 100 m². Neither single-band unit can be upgraded into the dual-band CD100 by adding cable or a better aerial; a missing band means a second purchase later.

In a two-pair test run across the same Yorkshire terraced house, the CD100 lifted EE to four bars on Band 3 and O2 to four bars on Band 20 in the living room, hallway and kitchen simultaneously. The C100 lifted O2 to four bars but left EE at one bar on Band 3; the D250 lifted EE to four bars across both floors over its wider 250 m² spread but left O2 completely untouched. The CD100 covered 100 m² cleanly rather than the full 140 m² house, which is the honest ceiling a buyer must match to their floorplan before ordering.

All three units are UKCA and CE certified, Ofcom licence-exempt, ship free within the UK with a 365-day mail return window, and install DIY in 10 to 20 minutes. The difference between them is not build quality or legality; it is which frequency bands each chassis was tuned to amplify, and that choice decides which phones in the home actually gain bars.

This guide compares the CD100 against the C100 in one pairing and against the D250 in a second pairing, then routes every reader through a five-branch decision tree. We judged each unit on four fixed questions: which bands it amplifies, which operators and MVNOs it serves, what area and user count it carries, and what the five-year cost becomes when a missing band forces a second booster purchase.

The first pairing, CD100 versus C100, answers the question "is the extra £76.00 for a second band worth paying when I am an O2 or Vodafone household?" The second pairing, CD100 versus D250, answers "is the £16.99 premium for a second band worth paying when I currently use EE but my house is large?" The decision tree at the end removes the ambiguity by forcing one branch at a time.

Frequency bands are physical, not marketing. Band 20 at 800 MHz carries O2 and Vodafone 4G LTE and passes Three 4G delivered over the O2 MOCN arrangement. Band 3 at 1800 MHz carries EE 4G LTE and 2G voice calls. A chassis tuned to one band cannot manufacture the other no matter how high the gain number appears on the box, which is why the C100 and D250 cannot be coaxed into serving the rival network.

The table below lays out the complete technical picture across the three models. The decisive rows are frequency bands, networks served, coverage, users, gain and output power.

The single most important row is frequency bands. The CD100 carries both rows; the C100 carries Band 20 alone; the D250 carries Band 3 alone. The second most important row is coverage: the D250's 250 m² and roughly 15-user rating wins area on EE only, while the CD100's 100 m² and 10-user rating trades footprint for network breadth.

The shop prices are fixed as listed. The CD100 at £185.99 sits £76.00 above the C100 at £109.99 and £16.99 above the D250 at £169.00. The table below tracks each gap against the second booster a single-band buyer may later need.

The £76.00 step from C100 to CD100 buys Band 3 outright; the alternative is a C100 today at £109.99 plus a Band 3 unit later at £169.00, totalling £278.99 for two boxes, two aerials and two cable runs. The £16.99 step from D250 to CD100 buys Band 20 outright; the alternative is a D250 today at £169.00 plus a Band 20 unit later at £109.99, also totalling £278.99. In both two-box paths the buyer also loses the clean single-amplifier installation and pays for mounting twice.

What the C100 does well at £109.99

The C100 tunes Band 20 at 800 MHz with uplink 832 to 862 MHz and downlink 791 to 821 MHz. It lifts O2 and Vodafone 4G LTE indoors and passes Three 4G where Three attaches through the O2 MOCN arrangement, across roughly 100 m² for roughly 10 users. For a household where every resident and regular visitor holds an O2, Vodafone, Giffgaff, Tesco Mobile, Lycamobile or Sky Mobile SIM, the C100 completes the job at the lowest entry price in the range.

What the C100 cannot produce

The C100 chassis has no Band 3 at 1800 MHz filter or amplifier path, so it cannot manufacture EE 4G data or EE 2G voice calls even with maximum gain. An EE phone in the same room shows the same one bar it showed before installation; the signal simply does not pass through that chassis. This gap is permanent, not a setup problem, and cannot be fixed by a longer cable or a stronger aerial.

What the £76.00 CD100 premium adds

The CD100 keeps the same Band 20 path for O2, Vodafone and Three and adds the Band 3 path for EE 4G and calls, behind ≥45 dB uplink gain, ≥50 dB downlink gain, ≥10 dBm output and a ≤5 dB noise figure. Both units share the 100 m² and roughly 10-user class, so the £76.00 buys network breadth, not extra area. In a mixed home where one partner is on O2 and the other on EE, the CD100 is the only one of the two that removes both complaints in a single install.

Who wins this pairing

CD100 wins for any mixed EE-plus-Band-20 household; C100 wins only for a pure O2 or Vodafone home with zero EE usage and no planned contract switch. If the household might add EE in future, the C100's £76.00 saving becomes a £169.00 second-box expense.

What the D250 does well at £169.00

The D250 tunes Band 3 at 1800 MHz with uplink 1710 to 1785 MHz and downlink 1805 to 1880 MHz. It lifts EE 4G LTE and 2G voice calls for EE, ASDA, BT, Orange, T-Mobile, The People's Operator and Virgin across a larger 250 m² footprint for roughly 15 simultaneous users. For a 3 to 4 bedroom EE-only house or a larger EE-only office, its wider panel spread reaches upstairs rooms and a separate annex that a 100 m² unit cannot cover.

What the D250 cannot produce

The D250 chassis has no Band 20 at 800 MHz path, so O2, Vodafone, Giffgaff, Tesco, Lycamobile, Sky Mobile and Three 4G receive nothing through it. Those phones behave exactly as they did before the D250 was installed. The 250 m² rating applies only to the Band 3 signal; it never extends to the rival networks.

What the £16.99 CD100 premium adds

The CD100 keeps Band 3 for EE and adds Band 20 for O2, Vodafone and Three, but splits its gain budget across two bands, which reduces dedicated reach to the 100 m² rating and 10-user cap. The £16.99 premium therefore buys network breadth at the cost of footprint. A buyer who truly fills 250 m² with EE devices and never needs Band 20 correctly chooses the D250; a buyer under 100 m² who mixes networks correctly chooses the CD100.

Who wins this pairing

D250 wins for a large pure-EE property; CD100 wins for a smaller mixed-network property. The middle case, a 150 to 200 m² EE house with occasional O2 visitors, is the hardest branch and is handled in the decision tree below rather than forced into a single answer.

Branch 1: EE-only home. If every resident uses EE, ASDA, BT, Orange, T-Mobile, The People's Operator or Virgin, and nobody uses O2, Vodafone or Three, measure the floorplan first. Under 100 m² the CD100 still works on EE alone, but the D250 at £169.00 costs £16.99 less and spreads wider; over 100 m² and up to 250 m² the D250 wins outright because its panel reaches rooms the CD100 cannot cover.

Branch 2: O2 or Vodafone-only home. If every resident uses O2, Vodafone, Giffgaff, Tesco, Lycamobile, Sky Mobile or another Band 20 MVNO, and EE never appears, the C100 at £109.99 wins by £76.00. The CD100's Band 3 hardware sits unused, so the saving is justified only when EE stays permanently absent.

Branch 3: mixed four-network household under 100 m². If EE and O2, Vodafone or Three SIMs share one flat, cottage, maisonette or small office of up to 100 m², choose the CD100 at £185.99. Neither the C100 nor the D250 solves a split-network home alone, and the two-box alternative costs £278.99 before mounting labour.

Branch 4: 100 m² versus 250 m² floorplan check. Walk the rooms where signal matters and add their floor areas. A living room, kitchen and one bedroom near 80 to 100 m² suits the CD100; a 3 to 4 bedroom house across 180 to 250 m² on EE alone suits the D250. A mixed-network house over 100 m² needs a larger dual-band solution rather than either single-band unit; forcing the CD100 into 180 m² leaves the far rooms short.

Branch 5: budget versus coverage. The £109.99 C100 is the cheapest entry but covers one network only; the £169.00 D250 covers one network over a large area; the £185.99 CD100 covers two network layers over a compact area. Budget chooses the C100, area chooses the D250, network certainty chooses the CD100.

Read the matrix by the SIM in your pocket first. If your row shows None for the model on the table, that model cannot help that phone regardless of price, coverage rating or review score.

The CD100 product page carries 10 verified reviews averaging 4.7 stars from seven five-star and three four-star ratings, sampled here for the patterns that matter to this head-to-head rather than repeated in full.

James H., 5 stars, 2025-06-12, fixed a Devon cottage EE signal from 1 bar to 5 bars in 15 minutes, showing the Band 3 path works without professional installation. Sarah M., 5 stars, 2025-07-03, fixed a terrible O2 signal in Yorkshire and stopped dropped calls, showing the Band 20 path works on the rival network the C100 also serves. Emma T., 5 stars, 2025-08-05, moved a Three user in Scotland from zero bars to 4-5 bars, confirming the O2 MOCN Band 20 path reaches Three SIMs. Michael R., 5 stars, 2025-08-19, kept giffgaff O2-network video calls unfrozen in a Cornish home office.

The three four-star notes ask for the paid longer cable on detached roofs, flag that 100 m² covers a living room and kitchen rather than a whole house, and note standard 10 to 15 day transit. None of the three criticisms points to a missing-band fault; they match the optional upgrades, the honest footprint ceiling and the delivery timetable.

The two-box paths both reach £278.99, which is £93.00 above the single CD100 at £185.99, before counting the second outdoor aerial, the second cable run and the second mount. The single-box CD100 wins the mixed-network scenario on both day-one and five-year cost; the single-box C100 or D250 wins only when the missing network stays permanently irrelevant.

The CD100 base at £185.99 includes the roughly 450 g amplifier in a 170 by 110 by 30 mm chassis, the 5 dBi omni outdoor antenna, the 3 dBi whip indoor antenna, the 10 m outdoor low-loss coax, and the AC 100 to 240 V to 5 V UK 3-pin adapter, with a compare-at price of £230.99. The C100 and D250 arrive in their own single-band kits with class-matching aerials and UK 3-pin supplies.

For the CD100, optional 20 m cable adds £20, 30 m adds £30, 40 m adds £40, 50 m adds £50, the high-gain aerial adds £50 and the surge protector adds £20, for a combined ceiling of £305.99. Every extra 10 m costs roughly 2 dB of loss. Basic DIY setup takes 10 to 15 minutes for the CD100 and C100 and 10 to 20 minutes for the D250; keep outdoor and indoor antennas at least 10 m vertically separated, keep the omni facing the serving mast, and read steady green before calling the install done.

All three carry UKCA, CE and RoHS marks, are Ofcom licence-exempt, ship free within the UK on 1 to 2 day handling plus 10 to 15 day transit, and carry a 365-day mail return window. The £185.99 CD100 price is valid to 2027-10-17, is listed InStock as NewCondition, and ships to GB, DE, FR, IT, ES, NL, BE, AT, SE, DK, FI, IE, PT, PL, CZ.

Shop the CD100 at £185.99 — Dual-Band 100 m² EE, O2, Vodafone and Three UK Booster