No. I've only been once and it was on an inset day, so probably not as busy as half term. 3 kids, 10, 8 and 5. It was hell. I'd also say most of it would be a bit young for a 10 and 13 yr old.
Just the queueing, queueing, queueing. 40 mins for a 5/10 minute activity. If there are only 4 people at a time allowed on an activity, and there 20 people in the queue already as an adult you can do the maths and work out how long you will be waiting, then maybe choose something with a shorter wait time. But the kids just didn't get it and those without adults with them were hardly getting to go on anything as they'd wait, then get bored, move to a different queue not realising that one was just as long.
No child management by staff, pushing in especially by school groups with not a teacher in sight, arguements, adults queueing in place of their child who was in another activity which I thought was particularly unfair.
My kids thought it was ok, the 5 yr loved it but I had to guide him the whole way as to which queue he should get in and keep an eye out for which queues were shortest of the things he might like in a tactical way.
They probably got about 6 activities each but that's cos we stayed until closing and it got much quieter in the last 45 mins or so, so they were able to jump on stuff with hardly and wait.
Had I just left the 10 yr old to find her own way round, she would have just wandered aimlessly for a couple of hours not deciding which queue to commit to.
If you're in London, there are far better things to do.