Newcastle is certainly quite a party town these days; lots of Irish stag and hen parties letting the side down there big time most weekends.
If you want a good place to go for lively social life at a weekend, with reasonable hotel rates, good food at fair prices and a friendly populace, Manchester is well worth a shot. Personally I can't stand the roaring, shouting and vomiting of gangs of drunk Irish people having "a good time" in cities in the UK and elsewhere, but if that floats your boat, Manchester is the place. Not as rough as Newcastle either, a lot closer to civilised!
Try the Britannia Hotel for special offers, right in the heart of things and no need for taxis. Great breakfast as well, if you're able to eat it!