I dont know the actuall legal position but I'm sure there must be stuff in there for such situations, for example you wouldnt want 82 year old policemen etc. The record company could argue that the show was a long term investment and as a stars age is relevent to the audience i.e. older stars dont appeal as much to the teens they might get away with it. I think its in jobs which have no reason not to employ older people i.e. sainsburys/desks jobs that this will really come into force.