You do have to have a timed slot, and tickets must be bought in advance. We had a 3.30 pm entrance but the crowds were relatively light and a broadcast was made that if you were ready you could go in. We spent almost 3 hours there. As others have said once you get through the small holding area, then into the cinema you are taken through to the main hall where you are guided. Sadly you don't spend as long here as you might like, then once through the Great hall you are free to wander. There is the green screen where you can ride a broom stick or travel in the flying ford. Kiddies can try using a wand, and the guides dotted around the area are a wealth of knowledge if you have a question. I used the audio guide as it gives you added extra information. Be aware though, prices are on the high side so if you have children get used to saying no. Hope you enjoy it, it was worth it in my opinion. Answer from exhaustedFareham on tripadvisor.com