The prices overall are fairly steep. Having seen the catering prices..
(then again, Brighton is not cheap generally unless you go to the right areas. It is not cheap on the seafront usually)
One suspects there will be offsite stuff/parties/etc but that'll probably mostly be on an ad hoc basis. I know of one offsite get together so far (gathered from another forum, so I'm not sure about netiquet)
But AWers will be all over the place - the trick is identifying ourselves! (as I said upthread, I know I'll be meeting some because I know what they look like...)
But generally every convo I have about WFC, or any con, starts or ends with the phrase 'in the bar' so you can't go far wrong if you lurk there!