This isn't even remotely true. Have you ever lived outside of London in the UK?
I live a few hours away from London by the fastest train and life is great. Free health care, great neighbours, the software engineer salary compared to many is very good, and there's loads to do. Cinemas, live gigs, local festivals, beautiful landscapes if you like the outdoors. There's just as much in the UK outside of London as there is in London.
There are many people who enjoy living in London, and that's great more power to them but non-London UK is definetely not "a non-place where only locals can live". I've moved around the UK loads and always been welcomed into new areas with friendly neighbours and such.