Yes, you are wrong.
West country and Welsh, yes, but not northerners.
There isnt just one northern accent anyway.
Liverpool, Newcastle and Yorkshire for instance, are all markedly different.

The northern accent thing is more just a north/south rivalry, more akin to America/Canada.

The simple fact is, over here, an accent does not effect popularity.

The two most popular soap operas in this country are Eastenders and Coronation Street.
One is based in the south, the other in the north.
They are as equally popular in their own region and their 'rival' region.

Me calling Eccleston a northern monkey, is the general insult to anyone from 'oop nort', just as they would refer to anyone from 'darn sarf' as a soft southern poof.

It certainly does not effect popularity on tv.
Even Welsh people have success on tv, and they are all sheep shagging cunts.