Signal/Bandwidth is not the issue
There's hardly anywhere near me, in the green fields of the East Midlands, where I can't get O2 signal.
Go me, eh?
But even with 3-4 bars, progress is slow and stuttery. I'm assuming because the number of people connected to a mast streaming videos and music is overwhelming the cable or microwave connection onwards from that mast to the network. Go to any event, whether it's a huge music festival or a smaller gathering, and you quite often get "perfect" 4G signal and "sod all" data.