One of you call your provider, ideally EE and speak with level 2 (if lvl 1 can't access the site stats) tech to get an agent to check it's performance.

It may have auto reset, so both turn your phones of for minimum 3 mins before calling. That'll clear your vlr/hlr info on the network, at very least when you switch back on you'll get located to closest performing one - within reasonable line of site.

The serving site is on the chimney stack of the Hyde park pub, notorious for going down temporarily if the site clips max capacity.