For transportation: Megabus
offers uber cheap transportation throughout the UK if you book ahead. And when I say cheap, I mean cheap
even for the UK. Germanwings
offer transportation to/from Germany and Poland. Poland is definitely worth the trip - it's beautiful, cheap and there's so much history there. Aushwitz (Oswiciem) would be worth the trip alone. If you like hiking, Krakow has some amazing mountains.
I am a total sucker for Germany and think everyone should go there. Food and beer is amazing. There are so many beautiful cities, especially the smaller ones. People are generally very kind. We caught a great swing band in Idar Oberstein one night.
Ireland's great. It's very pretty and there are palm trees. I think it's a very neat country, although the weather wasn't to be missed.
Dublin has a very good music scene. We went to Galway which was good for shopping and apparently geared a lot more to young people (we were camping a few miles away and didn't do much in the city).
Italy's gorgeous. There's obviously lots to see there as well. I didn't spend much time there so don't have much to offer.
Obviuosly, your ages won't be much of an issue. If you're looking for things more geared to young people, I would say college cities usually have a lot. Also, check out bulletin boards in hostesl (or if in another language, ask the reception [if they speak English]) about events, such as bands and what not.
As far as I've heard, trying real
absinthe is very difficult.