If you can't ask for contributions, I think I'd do 1) pizza, wedges, garlic bread, salad 2) sausage, mash and veg 3) veg curry, rice and naan breads 4) turkey pie, roasted new potatoes and veg 5) lasagne and salad 6) Chinese meal using some leftover turkey in the egg fried rice, sticky chicken wings and stir fried veg.
For breakfast: toast, muffins and crumpets with jam/marmalade
For lunch: make your own sandwiches, get cheese/ham/tuna/egg mayo and salad, plus crisps and crudités and everybody makes their own lunch if they're about.
I'd also start clearing room in your freezer and buying things when you see them on offer, ie half price pizza if you don't make your own, 3 for £10 on meat deals to get mince/chicken/sausages, garlic bread.
If you don't feel like you can ask for monetary contributions, at least ask them to bring their own alcohol, the food can be done fairly reasonably if you're organised but I tend to buy too much alcohol, ie someone liles baileys so I should get they, someone else gin, is 2 cases of beer enough, or should I get 3.....?