Little tip from Nigella (and personal experience!) about feeding masses: do fewer things, but lots of it.
If there are zillions of diff things on a buffet table, most ppl want a bit of everything so they don't feel they've missed out.
If you have fewer choices, but bigger amounts of it, a) it looks more 'feasty' and b) ppl end up taking less food as they won't want 7 spoonfuls of coleslaw or whatever.
Will it be a sit-down job or will ppl be milling around chatting and eating?
Cut things up into smaller than you think is necessary, but make shed loads of them ie baguettes 39p in lidl for 2, cut in half, topped with whatever and each half cut into 8 pieces = 32 mini sandwiches.
Chicken wings are cheaper than drumsticks - frozen even more so. Pre-cook and don't worry about the cellar issue - everyone worries but it's always fine.
Go to a butcher and ask for a massive bag of liver - then make your own pate to top your baguettes. For £3 you'll get enough liver to make a huge vat of the stuff!
A value tray of eggs (despite my hatred of them) are excellent buffet fodder - boil, slice in half, mash up all the yolks with mayo and curry powder and refill the egg halves. Always popular.
Good luck and don't worry :)