I waited 3 weeks for a test booking because 1 of the 2 Examiners was unavailable for a fortnight. There was a stand-in from another centre but lots of weather cancellations at the time which created another backlog. Could have taken a cancellation at short notice but chose not to. Cost me more to keep flying in the 3 weeks but that's life
CAA Examiners do IRs, CPLs, Instructor renewals, CAA Flight Tests (eg for candidates who have to prove that they can overcome a difficulty) and lots of other things.