Grimsby.
I lived there for three years. It's the most introverted place i have ever been. Almost everyone was born and brought up in Grimsby, everyone knows everyone else, very few people ever leave Grimsby and very few people move in. Grimsby people really don't like southerners and I was often referred to as a 'foreigner' and 'f--king southerner'. I was also often berated for the poverty with comments such as 'you southerners keep all the money and give none to us'.
The greatest irony was that I lived abroad until I was 12. We moved around several Asian countries and I didn't live in the UK until I was 12. I've also spent most of my life travelling. Yet Grimsby is the only place in the world I've been called a 'foreigner' and felt intimidated and threatened for being who I am!
The only other place I could never live is Milton Keynes. I'm from Aylesbury and I remember that whole area of north Bucks being beautiful and peaceful countryside consisting of little villages, open fields and winding lanes. MK is now a concrete monstrosity that's been plonked over that beautiful countryside. The place has no culture, character or history and everything is 'in your face' entertainment such as Bowl in the Dark tenpin, multiplex cinemas, the Skidome etc.
The last time I visited MK was in 1999 and my last sight was in my mirror as I drove back to Winslow. I decided at that point that I would never visit the dump again - and I've never set foot in MK since.