Impressed
I don't go into London at all, but at various locations around London - Gatwick airport and Bluewater Shopping Centre for example, I got 180Mbps and 105Mbps download respectively on my phone. That to me is far more than I actually need, and also rather surprising, since this was at busy times of day when I expected nothing much. I recently moved from O2 to EE and have been really impressed by the more or less constant 4G signal.