Difficult to advise you OP, because we don't know what the small Asda will stock.
I would just go there and get whatever they have.
Get a few big bags of crisps, bread sticks, carrots, cucumbers, peppers, cherry tomatoes and some dips like sour cream and chive. That way you've got some vegetable stuff on your table.
If they have any ready made salad things like Greek salad, tabouleh, coleslaw, get a few packets of those and you can empty them out into bowls.
Packets of ham and salami which you can arrange on a plate.
Things which can be served warm, like a pizza or two, a vegetarian quiche, a small rotisserie chicken if they have any, cocktail sausages, sausage rolls, samosas and onion bhajis if they have any Indian fakeaway stuff.
And for dessert, I'd get one or two ready made cold desserts like a trifle or something, and some fruit to cut up. You could cut up strawberries and bananas and serve them with some marshmallows and pretzels and a bowl of melted chocolate to use as dipping sauce.