As already said !!
Most of the time, i go the night before if at all possible!! Can see where you are coming from,, would make a more social event, before the serious bit starts !! Think its only the locals you have to convince ??
Can not really see it working at the Wellington site,, Not with "Pie & Pint" for a fiver, just down the road ??
Might work for the other sites ?? but can not see the numbers to make it viable
Probably works for HW events,, being on a Saturday night, Sunday event,, don't have to get away from work in most cases