LOL - I was going to nominate Slough too! It's one big industrial park - the rest of it is an afterthought. Even the name, short of course for Slough of Despondency :-), sounds depressing, the way you don't so much say it as let it fall out of your mouth.
As a confirmed Southerner, I don't know enough about Northern towns to comment on Hull or any others, but other Southern places I'd give "honourable" mentions to in the crap stakes are Dagenham, Basingstoke and Aldershot. Actually, Aldershot isn't so much "crap" as "terrifying".