Kind of stuff for sale and a question about Watchmen

Hi,
I have never been to a con before nor have i heard about this one before however if I get any money I will probs come up from Southampton for this however I just had a few quick questions really?!

In regards to the Watchmen directors cut viewings in Imax, is that pre-bookable or a first come first serve thing once you arrive.

And secondly what kind of stuff is gonna be on sale, is there gonna be loads of Marvel/DC/Vertigo/Image/etc comic back issues for sale...or is that not the kinda stuff that goes on sale here, i am a massive noob with this, so if anyone has the time to give me a quick answer that would be wicked

Thanks very much!

-Josh