Here is a crazy idea, nationalize them. Make it a single network with coverage everywhere. No more coverage that is only emergency services only. No more massively duplicate coverage in cities and barely any in the sticks, unless you happen to be on the one network that put a mast in the area.
I actually think the privatized model works well for telecommunications companies, but only with strict and heavy regulation. For the same reason as it works with supermarkets, it forces the networks to compete and ultimately keep prices down. But that regulation needs to prevent the large players from merging and buying up competition.
Masts and other infrastructure should be nationalized though, and any networks wishing to use the infrastructure would then have to contribute to funding it. Similar to openreach, but properly nationalized and truly neutral.
