You're off to Llangollen? Sweet! That's about a 20 minute (if that) drive from Wrexham, where I live. If you're after a 2 Litre bottle of pop it's gunna cost you about £1.50, but you might be able to get some cheaper. Dunno where you can find wifi in Llan (don't go there very often, although my auntie does live there) but Im sure there might be some place with it. The weather will be pretty bitter, either just frosty and cold or wet and cold. Make sure you have a decent coat with you. The beer.... really not sure to be honest as I dont drink beer (more of a spirits person) but I'll get back to you on that some time later, same for places to go as Im really tired and can't think at the moment.
Hope that gives you a hand, anything else you need to know about Llangollen and the surrounding areas just ask
it's a really nice place to go to and very Welsh (in a good way), so you should enjoy it.