All my buffets/ bbqs are gluten free
I generally do potato salad, as well as warm boiled/roasted baby potatoes with herbs and salt on, sausages, burgers, cold chicken drumsticks, coleslaw, a rice/bean salad. A cheese board and cold cut meats
The usual dips and crudités
You can get Pringle type crisps from Lidl (they aren't special gluten free ones, they just happen to be gluten free)
Morrison's do a great gluten free pepperoni pizza from the freezer, they also have mozzarella sticks and some great gluten free crackers.
I generally make my own gluten free sausages rolls, quiches and scotch eggs and pork pies but you can generally buy pretty good ones from M&S if it's just for one person.
The best gf bread buns you can buy are the warburtons gluten free super soft square rolls, they are very new so you do have to hunt for them. M&S ones will do if you can't find them.
A cheese board and cold cut meats
Just make sure people don't double dip in dips etc and let the coeliac go first before everyone else starts dropping crumbs everywhere and you should be fine.
I tend to keep anything that has got gluten in (e.g buns for the non coeliacs) away from everything else and separate some butter off as well. It's the gluten eaters that are treated as the pariahs for a change 