I think it depends where you order it from, we ordered one from Play.com and there was no deposit and they don't take the payment until it is dispatched, but I believe they have sold out now. I think some stores may require a deposit though.
Yes, the above answer is correct. It depends on where you go, really. Some places ask that you put down a deposit, in order to ensure you have one allocated.
Try GAME. They ask for a cash deposit (either �20 or �30, I cant remember how much exactly). Other places, like HMV also have a similar system in place. Ask the people in store, if you're not entirely sure, as each shop/site has a different policy.