As a Northerner who has lived all over the UK, I can say there was a bias against Northerners when I worked in the city, flat vowels were not especially welcome, I also notice a strange fear and confusion about the North from some Southerners, dyed in the wool prejudice about our 'flat cap' existence.
Conversely, many Northerners have a distrust of Southern incomers who tend to infiltrate the more desirable areas of the North with their Southern money after selling their two bed flat in Clapham and buying a 10 acre small-holding and opening a vanity business and pissing all over the locals with their fancy Southern ways.
I'm obviously on the Northern side of this divide (and there is a divide), I do think Southerners sometimes have strange ideas about the area North of the Watford Gap, I've experienced it, it ain't a fantasy, and Southern money from buying a very modest property can, when brought up north can distort a local economy quite badly.
However, there are some very cosmopolitan and exciting cities in the North, in fact, three out of five of the UK's major cities are in the North (one is in the midlands, but as a PP said, they largely go unnoticed).
I wouldn't say Southerners think they're necessarily better, but they do sometimes display hilariously ignorant views about their Northern counterparts which aren't shared the other way (as most people from the North understand the South).