Re: Mast sharing?
Yep. We actually only have 2 physical networks in the UK - MBNL which is EE and Three, and Cornerstone which is Vodafone and O2. Every other UK network is an MVNO to one of the core 4 networks.
The differentiation in coverage from the two vendors on the same physical network comes from the different spectrum allocated, in the main.
On this subject, I remember sitting in a pub in a village near where my parents live in Worcestershire. The locals were whining about the lack of coverage in the village on any network. (It was in a dip in a valley and although a few hundred houses had pretty poor coverage).
I informed them that both physical carriers had tried (and failed) to remediate this by putting a cell site in the bell tower of the church and both times the planning was denied by NIMBY rejections.
They were ‘well we don’t want a transmitter’ - I did try to explain that their only solution was a transmitter to provide service (funny that) and that the church would have made some money from way leaves too, but they didn’t seem very receptive to the idea.
I said as long as you reject the planning you won’t get coverage...