I agree - has prob been like this for a while since they were the first to offer 4G too (if I recall correctly). One of the reasons I switched from O2 to EE a few years back. I had been on O2 since first iPhone when O2 had iPhone exclusivity. From what I read around EE do seem to have the best and fastest coverage.
I can only speak for central London but the speeds I'm getting are 120MB/s upwards. So yes, very fast!