I'm going over with the guys from Rainbow Alliance.
Flight was like £100 including some luggage and £260 (plus a load extra for being under 25 but that might not matter to you) to hire a "golf or similar" for 4 days which should be good for the 4 of us.
Ticket for the festival itself is like another £110 plus some more (£60) for a camping spot with car space etc (thats the full Thurs-Sunday ticket its cheaper obviously if you go for less
EDIT: Car hire is 5 days actually - Thursday to Monday