I'm treated with suspicion too. A lot of it is 'not from here [the village/town/county]' (and not sounding like you're from here) rather than 'not white' or 'not from the UK' so I can't hard agree it's strictly xenophobia/racism etc.
And your anecdote about that guy: exactly what I'm saying. Everyone out for themselves. Selfish. Unrelated to racism or xenophobia etc
But are you saying in London everyone falls over themselves to hold open doors, let you skip queues, always waits for people to get off the train first, nobody barges past anyone, every single shop worker says "hello good morning" "thank you" "have a great day"...? What acts of making you feel welcome exist in London that doesn't elsewhere in the country?
edit: And you started "I agree...but not with the unfriendliness" then ended with "London can be unfriendly" so I'm a bit confused :D