I'd recommend the Brit guide book too. very, very useful.
another thing with the disney parks - the park photographers. When they take your picture as you're meeting the characters etc, they give you a small card with a barcode on it (to track the digital picture they've taken).
Don't think 'won't buy it anyway' and throw it away. Keep the 1st card you get. After that everytime they take a picture, you can give them that card, and your pics will be added to it.
You can view them in any disney park on the monitors in the shops, or wait until you get back to the UK. You get 30 days+ to view your pics online, and can then order any you like. Postage to the UK is only around $5-10.
I managed to take some nice pics myself, but you'll get some very good group ones from the Disney photographers, and in the waterparks it's much better than risking your camera getting a soaking.
hope that makes sense. The Photo Albums they can produce for you are excellent.