Not helpful at all to your post, but I've just been to this last week and it's fab! I'm not the biggest HP fan, but the tour is brilliant. I wouldn't bother with the digital guides though, I booked them and we never listened to them other than the 1st bit before we went in. The photo/DVD green screen experience is really expensive, as is the merchandise. I'm bordering on bankrupt as a result . Hope you enjoy!
I stay (yes, present tense, we've been twice!) at the Holiday Inn Junction 8. The hotel has a pool, which ds loves. Quiet despite its proximity to the motorway and only about 10 mins from the studio. Last time they were having an HP themed weekend and showing the films in the lobby with free squash and biccies for all.
I paid 40 quid for the photos. This was 3 photos of ds on his broomstick (and one in the Ford Anglia) and a memory stick with a video clip of him riding his broomstick around various HP locations. The video absolutely made it for me, the photos I can take or leave but you can't just buy the vid (I don't think).
My top photo tip: the green screen bit gets very busy by early afternoon. I would advise getting to it as soon as you can and then backtracking round the rest of the sound stage. Once you leave the Great Hall you have the run of the entire first sound stage, you can go around in any order (once you've left you can't go back in).
ds and I missed out on the green screen bit first time around because the queue was about 90mins long by the time we got in at 1:30-ish. This time we were on the first tour of the day and we completely overreacted, charged straight over to them (they weren't really expecting anyone for about 10 mins!) and ended up having the entire area to ourselves - there wasn't even anyone else using it by the time we finished