Went to this with my 2 kids today. Be prepared for a long session as parents wait in a holding area for the 6 hours or so that the kids are in (to make a 30 min show!). There's a Starbucks concession for you to *buy* refreshments, or you can leave and go elsewhere if you want (which surprised me). There's a live feed from the studio so you can watch the goings on.
Audience numbers are around 40, so it's fantastically intimate, and they all seemed to get to chat with Hamster a few times during the afternoon and will hardly be difficult to spot on TV with so few people there.
Yes, they overbook, and yes you have to be there suitably early, but that's the deal with all the free TV recordings. Why do these shows overbook? Simple - plenty of people won't turn up, especially as they've paid nothing, but the producers need to fill the audience seats, and it looks rubbish to have empty seats. I too was turned away from Elstree the other week ("Are you smarter than a 10 year old") but took it on the chin and went back on Tue to another recording, but got there a little earlier. Bit tough telling your kids that you're going home when you don't get in, though.
I'd recommend going, but make sure you get there early! Our researcher told me they turned away some 30 people this morning! Not so many this afternoon, but still a few - though they did cut the timing well too fine... At least in central London you can go and do something else instead.