Interesting question, actually, and I see where you're coming from, as US films (however good the writing may be) tend to be written to American speech rhythms and can sound odd when delivered in English accents.
Being of Northern heritage myself, I appreciate that there's Northern and Northern and what might suit you if you're speaking with a Yorkshire accent won't suit you necessarily if you're from Oldham. But, in general terms, I imagine there are lots of good TV writers, in particular, who have written solid pieces based in the North. The big problem, these days, is that there is less good drama writing about for TV than there was in, say, the 1970's and 1980's, and you don't necessarily want speeches that are a bit outmoded.
Also, a lot of Northern British TV (and film) writers seem to specialise in fairly intense, downbeat drama, which isn't to everyone's taste, but still good writers might include: Jack Rosenthal (as mentioned), Willy Russell (some overdone, but his TV work is less well known), Mike Leigh (who is perhaps the obvious choice for film related 'Northern' material), Paul Abbott (more of a modern name: 'Clocking Off', 'Shameless'), Debbie Horsfield ('Making Out', 'Cutting It' etc.), Jimmy McGovern etc. I am a long standing fan of Peter Flannery's 'Our Friends in the North', but that's very specifically set in Newcastle.
'Film' wise, I think you'll find that it's very similar writers who have tended to produce home grown films - Simon Beaufoy, who wrote the screenplay for that famous piece of Sheffield set comedy, 'The Full Monty', is not incidentally from Yorkshire, 'Billy Eliott' was from Newcastle born Lee Hall, 'East is East' from Salford born Ayub Khan Din. However, these films tend to be very specific in their casting, and haven't necessarily been followed by less well known material also set in the North from the same directors, and I would assume you'll get better chances from scouting through the TV material!
Of course, all this presupposes that you want to work from a specifically 'Northern' oriented script - you may not have to do that, but I can understand why you think it may be more appropriate for your patterns of delivery!
Naturally, in Hollywood, they know nothing of any of this - I'm not convinced they would even be able to recognise what a 'Northern' accent is! ;)
