I don't watch it (can't abide it - it's just a guessing game after all) but I would assume like other pre-recorded shows. there is a voice over at the end done by the continuity announcer or a banner across the screen which is just slotted in over the prerecorded programme.
what I want to know about is who are these people who play? There are some that have been there for WEEKS, don't they have jobs or lives? How does that work?
Kelibug
My friend was on it back in april and he had to ask for leave from his job to go down to Bristol to film it, he was there for about 20 shows. But came away with 13k so all worth it.