Amsterdam - Amsterdam is cheap and easy to get to. Never been myself, but I get the impression the place is geared up for folks like us in more ways than one
Barcelona - I was supposed to go last year with the infamous M.

The flights we booked were cheap. The accomodation less so, in fact it was rather expensive. Also not sure it's geared up for revellers like us miniminers
Budapest - as above
Dublin - Cheap to get to. Accomodation expensive. We've been there already though ..
Dubrovnik - Didn't get much interest in Bruges, so changed the option to this, if thats OK? Never been to this one either.
Hamburg - Cheap to get to. Accomodation cheap. Lovely scenery. Great in December (Xmas markets). Not geared up for night life IMHO, unless your name is Sting .... need I say more?
Madrid - substituted for Talinn. Hope y'all didn't mind? No opinion.
Marrakech - Cheap to get to. Dirt cheap accomodation. Night life is fab. Great weather all year around. If there are enough of us, hire out a whole Riad at circa £15-30 per night.
Palma - never been. No opinion.
Prague - as above. Never been, but I've heard it's wonderful for a bunch of giggling girls and guys