Comfort food can be either.Depends. If you mean something simple, filling etc, you can't go wrong with Beans on Toast (with my added specialty ingredients) or Heinz Tomato Soup with wholemeal broken up in it.
If you are meaning feeling-crap-and-fancy-a-treat, Cadburys Caramel or a Crunchie! Or possibly Tyrrells Sweet Chili crisps.
I feel hungry now...