Hmm I guess that rules Cannibal Corpse and their support out of this announcement as their UK dates start on the 13th. Although a couple of their dates are sold out already so maybe it won't impact ticket sales too much.
The only other tours I can see ending on the 13th are Venom Inc, Satyricon, Suffocation and Nervosa but with Venom Inc announced already I don't see why they'd hold off on the others.
To be honest there's so many bands that are playing Summer Breeze and Graspop that could possibly turn up that I have no idea anymore
It will probably just be small Sophie bands.