We have scallops in the UK too - a slice of potato about the same size and shape as a hamburger, deep fried in batter. Anything that you'd put on your chips (that's proper chips - not crisps, not french fries, but proper chips) is good for a scallop - so salt and vinegar are totally acceptable as are mushy peas. Tomato or brown sauce is ok; curry sauce or gravy is pushing it but not uncivilised. wtf is ranch dressing?