No network wins Colchester on coverage. All four are within 2 points of each other in Ofcom's measurements, across 829 addresses sampled in 47 postcodes. On a difference that small, EE, O2, Three and Vodafone will all work here — so choose on price, contract length and roaming, not on a coverage map. Coverage only becomes the deciding factor once you leave built-up areas, and it still varies street by street indoors: check your own postcode below to see the measurement for your address rather than for Colchester as a whole.
Ranked by Ofcom's overall score: Three 99, EE 98, O2 98, Vodafone 97. The spread between best and worst is 2 points, which is inside the margin where a coverage figure stops being a useful tiebreak. Ofcom's data describes outdoor signal across sampled addresses; it cannot tell you how any of them behave inside your own building.
These scores for Colchester are Ofcom's own measurements, taken from the Ofcom Mobile Coverage API (May 2025 data) across 829 addresses in 47 postcodes. They describe outdoor signal at sampled addresses across the whole of Colchester; signal inside a specific building, and on a specific street, can differ from the area figure.