Where can i get Harry Potter and the Deathly Hallows part 2 midnight showing tickets?

If there not all sold out i was wondering where I could get tickets to
the midnight showing at the IMAX for harry potter and the deathly
hallows par 2. I've been looking for ages but can't find anything.
Please can someone help me out? I only need to tickets.
Also I live in England so probably the IMAX in London or something but
i don't mind traveling a bit.

Thanks
(i'll pick a best answer)