Since last Sunday you've been able to watch Attack the Block on LOVEFilm Instant.
Tonight Joe Cornish, Alex Esmail, Nick Frost and briefly, Edgar Wright sat on a sofa at Big Talk's London headquarter to waffle their way through the film while it streamed and answer Chat Room and Twitter questions. I believe this was the first time LOVEFIlm had attempted such an event and it seemed to be a great success.
The whole Q & A was once available to watch at LOVEFilm but now it says "temporarily removed". There are some photos here.
Here's a link to the costume Joe refers to