If you are a Dr Who fan you already know this one, but they refer to thin rectangular pieces of breaded fish as “Fish Fingers”. I guess it is no more unusual than our calling thin fried pieces of chicken as Chicken Fingers, though I haven’t seen chicken fingers on a UK menu yet.
I did also buy custard, though I haven’t tried it yet. And for the record Matt Smith wasn’t actually eating Fish Fingers and Custard in Dr. Who, though he later did on the Graham Norton show (9:37). FF&C is not a normal British thing.
I also found some cookie like things called Chocolate Fingers. They weren’t very good.