I wonder what Download France will be like? They'll be selling day tickets for €66 (about £50) from Friday. My last Donington day ticket cost £80, and they didn't go on sale until something like February/March. Accommodation was a nightmare, though, most of it was booked up long before the day tickets went on sale and cost a fortune.
Edit: Donington is selling day tickets from this Friday today, but only a 'limited number'.
Edit: Donington is selling day tickets from this Friday today, but only a 'limited number'.