Honestly don't waste your time or money - I second that.
Kraft/Mondelez have really run the place down. The 4D cinema is a decent addition, but ripping out the actual production (you won't see any real work happening) and removing all trace of the Bournville/Cadbury history since we were last here before the take over says it all really.
Cadbury world is a total rip off. There is nothing inside except queue lines. Even the chocolates in their own shop are damn expensive. Save your hard earned money.
Went a couple of years back. The family enjoyed it alot and I still have fond memories of it - the history of it all was fascinating. However yes there were queues (not more than 30-45 minutes) and timed entry to one area.
I remember they said you could make the chocolate bar of your dreams or something like that, reality was a plastic cup, some melted chocolate and you could pick 1 topping from about 8 I think. That was the biggest let down for me, which is astonishing really, considering how crap it is anyway.