Try the Magic Flute, it looks really odd from the outside, but it's a lovely room (if a bit shabby, but looks great with the lights low). The woman who owns it is a bit strange, but if you're doing your own catering you should be OK. Don't think they'll charge for you bringing your own booze either.
Magic Flute Banqueting Suite
31 High Street
Haringey
London N8 7QB
Tel: 0208 341 7120
We held our wedding reception at the British Legion in Muswell Hill, although not too pretty from the outside, it has a lovely bright room with a small bar and kitchen.
The staff are absolutely fantasic, freindly and helpful and it is not expensive.