Mobile networks are very variable, there are of course locations where one provider works and others don't.
The latest reports suggest generally it looks like EE continue to offer the best coverage. Three offer the highest speeds, but this tends to be in urban areas. Vodafone are third place. O2 are struggling, but there's some evidence they're recovering. This has been the pattern for a while. Which may change if Three and Vodafone merge.
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Note that with EE, sub-providers that use the EE network don't always get the same coverage. EE use several frequencies, but band 20 is the one that provides their best rural coverage. But many of the sub-providers that ride on the EE network aren't allowed to connect with band 20.
The latest reports suggest generally it looks like EE continue to offer the best coverage. Three offer the highest speeds, but this tends to be in urban areas. Vodafone are third place. O2 are struggling, but there's some evidence they're recovering. This has been the pattern for a while. Which may change if Three and Vodafone merge.
Broken Link Removed
Note that with EE, sub-providers that use the EE network don't always get the same coverage. EE use several frequencies, but band 20 is the one that provides their best rural coverage. But many of the sub-providers that ride on the EE network aren't allowed to connect with band 20.