Research found that postcodes in bigger cities – including London, Nottingham and Glasgow – enjoyed the best mobile coverage. · Tim Robberts via Getty Images
From full bars to patchy service, research from consumer group Which? has revealed the UK’s best and worst areas for mobile signal quality.
Which? said its mobile network quality map – powered by network insights provider Opensignal – uses real-world data from consumer mobile handsets to create a percentage score for how consistent the signal is in each postcode area in the year to August 2025. It looked at the signal quality across the four major networks – EE, O2, Three and Vodafone (VOD.L) – to generate an average overall score.
Perhaps unsurprisingly, the research found that postcodes in bigger cities – including London, Nottingham and Glasgow – enjoyed the best mobile coverage.
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The SE11 postcode in London – covering parts of Kennington and Vauxhall and located just across the Thames from Parliament – and NG3 in Nottingham came in joint first place for best quality coverage. Mobile users in these areas experienced good connection 87.8% of the time on average, according to Which?. It found that all of the “Big Four” mobile networks delivered consistent connections in both areas, with scores of 85% or higher.
London’s SW3 postcode, which covers the affluent areas of Chelsea, Brompton and parts of Knightsbridge, also featured in the top 10 with a score of 86.8%. Another postcode in London which got the same score was SE27, which incorporates West Norwood, as well as parts of Gipsy Hill and Norwood.
Postcodes in Romford, Glasgow, Bradford and Sutton were also among those featured in the top 10.
Meanwhile, postcodes in Wales and the South West were rated as having the patchiest and most unreliable mobile experiences in the UK.
SA70 in Tenby, Wales, which is a popular seaside tourist destination, was ranked as the worst postcode for mobile network quality. Mobile users in this area only experienced good connection 54.3% of the time on average. Which? said that this dropped to 38% for Three customers, while EE and O2 customers enjoyed the best mobile quality in Tenby, with score of 71% and 63% respectively.
LD1 in Llandrindod Wells, Wales was ranked as the second-worst postcode for mobile network quality, with an overall score of 54.8%. Which? found that Three was the worst network in the Llandrindod Wells, with customers experiencing a good connection just 41% of the time. O2 customers were found to have the best experience, with a score of 66%.
In England, TA5 in Taunton, Somerset and TR4 in Truro, Cornwall had the worst postcodes for network quality, with scores of 56% and 57.8% respectively. Which? said that O2 was the patchiest network in both areas while EE provided the best connection. Two other postcodes in Truro – TR27 and TR 18 – were also in the bottom 10 postcodes.
Natalie Hitchins, Which? head of home products and services, said: “This research shows just how dramatically the quality of mobile coverage can vary across the UK.
“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? highlighted that virtual network providers, such as Smarty, Giffgaff and VOXI, each piggyback off one of the Big Four networks, and so users should generally expect similar quality to the parent network.
In addition, Which? pointed to its previous research which found that smaller providers outperformed bigger rivals in several areas, especially on value for money. The consumer group said that rolling monthly Sim-only contracts for the Big Four networks start from £19 whereas these are available for less than £5 from some of the top-performing smaller firms, with more data included.
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