I connect to the Primary School as it is a few 100m away from my house. No need for an outside installation. Have a windows facing the mast, and there are a few occasions where I have no signal, but it is usually as you say ... lots of bars but no data coming in.
I did complain just before the lockdown and was told others had complained and the outsourced tech company was looking in to it. I explained it seemed to get worse as the day went on and came right late evening, and they said that it is the common complaint. It then got ok for most of the lockdown, but has gotten up to its old tricks in the last week.