Which? data exposes sharp UK postcode gaps in mobile signal quality

Which? has released analysis of real‑world mobile handset data showing large differences in the quality and consistency of mobile connections across UK postcode districts, with some rural and coastal areas delivering good connections only around half the time while central urban districts enjoy consistent service nearly nine times out of ten.

The consumer group compiled handset measurements up to August 2025 to produce a percentage score for how often users in each postcode experienced a “good” mobile connection. The results show postcode districts in Wales and the South West among the most unreliable, while several London, Nottingham and Glasgow districts scored best. "This research shows just how dramatically the quality of mobile coverage can vary across the UK," said Natalie Hitchens, head of home products and services at Which?. "Choosing the right provider can mean the difference between seamless coverage or constantly battling to make a call from the comfort of your own home."

Which?'s district averages are built from data contributed by consumer handsets on the four major networks. At the lower end of the scale, SA70 in Tenby, a popular Welsh seaside town, recorded the poorest overall experience with a district average of 54.3%. Network performance varied within that postcode: customers on Three had a good connection just 38% of the time, while EE and O2 users experienced better connections, at 71% and 63% respectively. LD1 in Llandrindod Wells was the second‑worst postcode, with an overall score of 54.8% and a notably weak showing from Three at 41%.

Several postcodes in and around Truro and Taunton also appeared in the bottom 10, illustrating persistent patchiness in some parts of the South West. Other low‑scoring districts included DY13 (Dudley), SA31 (Swansea), ME19 (Medway) and IP17 (Ipswich). Which? said seasonal visitor hotspots such as Tenby can see large fluctuations in demand that expose underlying coverage weaknesses.

At the opposite end of the ranking, SE11 in London, covering parts of Kennington and Vauxhall, and NG3 in Nottingham tied for the best quality of mobile coverage with district averages of 87.8%. In those areas all four major operators—EE, O2, Three and Vodafone—delivered scores of 85% or higher. Other top performers included RM5 (Romford), IG2 (Ilford), WD24 (Watford), SW3 and SE27 (London), G13 (Glasgow), BD3 (Bradford) and SM3 (Sutton), where users generally experienced a reliable connection.

The findings highlight a distinction between coverage availability and connection quality. Network providers often advertise national coverage figures—for example, claims that 99% of the UK is covered—but Which? emphasised that availability does not necessarily equate to a consistently good user experience in every local area. The consumer group recommends that people unhappy with their mobile service consult its free mobile quality map to compare provider performance in their postcode and consider switching providers when contracts allow.

Which?'s dataset covers user experience through August 2025 and is based on aggregated handset measurements; the organisation said it selected metrics intended to reflect how often consumers can make calls, send messages and use data without significant degradation. The analysis also underscores regional variability in operator performance: in some districts one network outperformed rivals by a large margin, while in others the major providers delivered similar results.

Mobile coverage and quality remain priorities for regulators and policymakers as the UK continues to upgrade networks and roll out new sites. For consumers, the Which? data offers a locally focused tool to assess which network is likely to provide the most reliable service in their area and to inform decisions about switching providers or pursuing remedies with current operators.