The longest I remember was over 1h for Rick Stein's fish & chip restaurant in Padstow. Fantastic fish & chips, though. And this time, we were prepared for the wait (although it only took 40m).

Most places here are quite pragmatic about it and will happily take a mobile number and call you when there's a table for you. You can then wait in the pub over the road, and it doesn't seem such a hassle - particularly when you expect it.