Look on the Dibb website. They have lots of info there.
We are just back from there it was fab, just like walking into the HP world.
I think you will have to buy a ticket for Universal for both parks (Islands of Advernture and Universal) as the HP world is over 2 parks. You get the Hogwarts train to from one area to the other, or walk to the other park.
There are lots of ticket sites which do tickets cheaper than the parks, We got '2 week' tickets which was cheaper than just turning up on odd days over the hols.
If you are going there anyway you really have to go to HP, the Gringots ride is amazing (not a rollercoaster) we didnt do the Dragon Challenge one as I cant do rollercoasters
but you can go through in the queue and see all the stuff on the walls of the rooms (both have long queues quite quickly so go early) and then just leave...
I could prattle on about it for ages was completely blown away but I am a sucker for stuff like that 
Just a heads up, if you havent been before it is really hot just now, even the locals were commenting on it. It hit 100 degrees on one of the days, rest were between 80 - 90's. In the 70's at night even with nightly thunder storms which usually clear the air here
Nothing prepares you for that wall of heat as you walk outside
factor in lots of drinks in budget, get a refillable mug at park it seems a lot but you will get your moneys worth even if you just use them for water (bottled water soon costs a lot and the water in the drinking fountains is warm)
The fish and chips in 'The Cracked Cauldron' is good!
Have a great time you wont regret it if you go.