Ooh and onlylivingboy thank you for going to the bother of finding out the fees for me. 
I was wondering whether sometimes, certain celebrity contestants such as, say, just picking a name out of the air like, Johnny, might have budgeted both tax-wise and time-wise to only be in the programme up to a certain point. Eg "well I'll do this but I am not likely to be the greatest and probably won't get to the final, so that's £40,000 in the bank with me tied up to the middle of November and then I'll get my agent to book me a load of lucrative after dinner speeches during the busy time in the run up to Christmas, won't be a problem as my Saturday nights will be freed up by then," sort of thing.