Thanks David, a useful site.
EE is what used to be the BT network I think? They appear to have overall the most coverage but when you zoom in there are areas where their coverage is not good and one of the others is better.
Since my first Smart Phone, I have always bought a dual-SIM phone, and put the two major networks into the phone, for exactly the reason that coverage varies from location to location. When I travel over to the UK I can roam to more than one of these networks on each of the SIMs I have installed here in Germany, so except in areas where NO network has coverage, I’m usually OK for spotting myself from a summit. This map will enable me to know which network I should roam-to to ensure I have coverage from a specific summit, thanks.
73 Ed DD5LP/G8GLM.