I agree with the breakdown of the social contract in London, but not with the unfriendliness. I've lived in the UK for eight years and have travelled to many parts of England and Wales.
I've never felt as unwelcome in London as I do almost every time I leave it. Constant suspicious looks, questions about who I am and what the purpose of me being there is, the occasional downright xenophobia.
To give you a recent example, just a couple of weeks ago I was in a supermarket in Bangor stocking up on some water ahead of a hike in the Lake District. My train was delayed, and I am now about to miss the last bus for the next two hours (still needed the water). I explain this to the guy ahead of me in the queue, asking if I could maybe jump ahead of him. He looks at me, says "No", laughs, and then proceeds to scan his items as slowly as he can. Not everyone is like that, but this kind of thing happens all the time.
I definitely believe that you'll feel more of a sense of belonging outside London if you're a local, but as a non-local, it is not friendly at all. And the further away from Britain you are from (geographically and culturally), the worse you are treated. I noticed the difference in reaction when I told people I am Moldovan compared with my ex-partner telling them she is Dutch, and my non-white friends tell me stories that are even worse. London can be unfriendly and isolating, but I'd never live outside London and a few of the other cosmopolitan cities.