you'll find it hard to find a pub that will let you bring in wine and fruit and mix up sangria behind the bar, but maybe one of the local bars like the king's Inn? thay have an upstairs room.
otherwise, how about somewhere like the MACRO centre on North King Street? they may have a licence.
Thinking about it, i'm not really sure if you can really hire a room someplace and then serve alchohol without a licence. so maybe a pub is your only option. in which case you'll have to change the format a bit from the usual.
the sangria night always seemed to cause problems in Bolton Street. is it not possible to hold it in the S.U.? they are kitted out similar to a bar, having all the required exits and the like. i always wondered why they never beacme a bar, most of the other colleges have one.
is there a chance that this new "health and safety" regulations that they talk about are a bit of a ruse to get the event out of the building? it'll be interesting to see if they can still hold the wine receptions and the like that they used to hold after events like the travelling scholership forum, interact awards, and thesis results, or if it only affects events involving sangria.