It's official re: Essential Festival - check out http://www.essentialfestival.com/
for more details:
"It is with very sad regret that Essential Entertainments are announcing the cancellation of the forthcoming Essential Festival due to be held over the 3rd and 4th August in London¹s Hackney Marshes.
Essential have made this very difficult decision after considering a number of issues in the build up to the event. The disastrous Rock Day at Bristol¹s Essential Festival has created significant financial difficulties for the event, which have not been able to be sufficiently resolved. In addition to this, the site suffered considerable damage after the adverse weather conditions that Mardi Gras had to face last weekend, with the result that Essential are not wholly confident that the location would be suitable for hosting the festival.
This year has also seen a substantial slump in the market for outdoor events, with the notable exceptions of Glastonbury and Oasis, with many of the major events being subject to low attendance."
So, I'd ask for a refund if I was you!