Some people might like something light, so I'd go for a buffet so people can help themselves:
Loads of salad - leaves, cuc, radishes, mustard and cress, baby tomatoes, pepper rings with dressings served on the side
Potato salad and coleslaw - home-made is nice, but if you provide shop bought ones no one will mind!
Jacket potatoes with cream cheese served on the side for those who want it
Plus as many of the following as you think you might need:
A whole cooked ham - cooked yourself or shop bought
Turkey slices that have been left over
Selection of cheese with crackers, grapes, celery
Quiche
Large whole pork pie with cranberries on top (supermarket deli counter)
Smoked salmon - so easy, you just open a packet and arrange on a plate!
Slices of Christmas cake
Mince pies with cream, brandy butter, custard or ice cream (or all four...)
Large plate of fresh fruit or a fruit salad in juice
Enjoy! 🎄