riiiight...first up, "may not make it up to the UK?!?!?, said wot? its only a 2hr flight from Barcelona.
anyway you arrive end of june, so unfortunatly you will miss Sonar festival (Barcelona) but barcelona generally is a great city any time of year, they also got some good sneaker shops.
if your a bit hardcore, and like electronic music Monegros festival is up there as one of my all time favorites (normally mid july about 3 hours west of Barcelona, 22hr rave in the desert, dont wear ya good sneaks, they will get phucked up)
as mentioned above, Ibiza is also good for a week of caining it, not been myself yet as i prefer city's to holiday resorts.
Exit festival in serbia is also good 7th-10th july
the Garden festival in Croatia is on that same weekend (6th-13th, some mates went last year, said it was great)
Dance Valley in Amsterdam is well worth a visit thats on the 6th aug, can reccomend a stay in citizenM hotel.
other than the obvious dutch attractions (tulips and windmills) Awakenings also do good partys in a gas chamber just outside the city.
Berlin is really cool anytime of year, festival wise NatureOne 5th-7th august.
just recently went to Wroclaw in Poland, really nice city and a few universities so has good nightlife, apparently Krakow is just as nice.
London, you know you gotta. notting hill carnival at the end of august, SW4 festival on the saturday before carnival is a good warm up.
most of the big festivals in England sell out really fast, so you probably wont be able to get tickets while your over here, the european ones seem to be easier to get tickets last minute.
Italy has never really interested me, ive heard milan is nice.
Paris, hmmm , would be ok if it wasnt full of french. but if you like expencive, smelly places that are full of arrogant people then you'll love it.
I think you should do , Barcalona, London, Amsterdam, Berlin and one of the eastern european city's.
give yourself a few weeks in spain, a couple of weeks in England, long weekend in the Dam and a week in Berlin and a week in poland or latvia or summin.. if you book ahead travelling around europe is stupidly cheap, ive gone to berlin just for the night before, straight from the airport to the club, then cab at 8am and back to the airport, on a plane, and home in time for a sunday roast
when you decide on what city's you want to visit we can all go into alot more detail on what should be seen and what should be avoided, cheap airlines, places to stay etc etc.