I've been told that in Mock the Week, the same bits are filmed several times, which can sometimes be a bit wearing for the audience. But it means the show can be edited to look just as they want it and with the best takes. And lots of the rounds have a stand-up element, so I've heard lots of direct lifts from a performer's stand-up routine. Still, it's a good showcase for them.
I don't think scripted is the right word, but there must be a lot of decisions made before the show gets underway. How far those decisions go, who knows? At the end of the day, the shows are meant to make us laugh, not to act as a beacon of truth. And as far as I'm aware, they don't claim to be unscripted anyway.
I don't know if I'll laugh or cry if the newspapers start writing stories about a 'faked' and 'misleading' comedy show. How about an in-depth investigation in just how meaningless Dara Ó Briain's giving out of points are on Mock the Week...?