They won't deny an ad. Only downside is that costs money. But, if one was able to communicate with the other artists who played to see who else got screwed over, in addition to possibly exploring connects to find artists connected to scenes that the Creamfields folk considered big enough to sign on to the ad in support, you'd have some big leverage there. Perhaps something worth exploring if the other approaches end up being dead ends and your check doesn't show up. But, hopefully they stick to their word in the most recent communications.