'Technically, not a town' as in London - well I think 'technically' neither is York. Can't say I've lived there but it's lovely
I'd nominate my hometown of Bedford, a crap town centred in a region of crapness. I left there running when I was 18 and have not seen anything but decline since, especially since the rather crappy city of Milton Keynes closed down half its amenities.
When WHSmith is the best shop in town you're in trouble.
(My data may be out of date there but it was by far the biggest shop in the Harpur centre when I was a lad and when I tried to go shopping there a couple of years back we gave up and went to MK on the way back to Wales)
To be fair though - Stevenage, Letchworth, Biggleswade etc nearby.... oof.
I'm impressed someone likes Newport - I suppose someone's got to.
And Birmingham... where is Birmingham? I enjoyed living there but it's not exactly seen as the apple of the UK's eyes.
Now Scotland, as Feanor rightly says - I used to live in St Andrews, pretty crappy unless you like golf but in the local neighbourhood - Dundee, Glenrothes and Kirkcaldy - but my favourite crap town north of the border would be the hole my cousins once lived in - East Kilbride. Rarely can you beat the newtowns for crappiness.