New Forest/ Bournemouth/Bristol
loads of party venue's in these surrounding areas..
there's a good beach party outdoors in Bournemouth (near Sandbanks)
New Forest (loads of areas, huge forest to have it in) near Southampton airport
Bristol (just South of the city there's a woodland which has some of the UK's best party atmosphere's) also has easyjet flying to its intl airport... (cheap like the budgy...)
failing that I could find out about partys in the sussex area, Gatwick Airport close by, even cheaper for intl dj's, and people flying from one end of Britain to the other...