I think there is some confusion here regarding the shipping schedule. Actually, the confusion is that there even is a schedule. July was just an informal thing they stated on the forums here and elsewhere. The actual contract doesn't stipulate any shipping schedule at all, and so it is impossible for them to be late per the terms of the contract.
At best, the contract says they will HOPE to ship by Q2 or Q3. I.E, as late as September 30th (obviously they missed Q2 already). Even then though, it doesn't state they will for sure ship in September, just that they hope to.
I'm afraid brian is right about the due date. They can only really be held accountable to what they have put in their T&Cs and that is "hope to achieve Q2/Q3 delivery". But they gave themselves a massive get out clause when they revised it. This clause was not in their original T&Cs so you need to get a copy of what you signed up to and when. Their later T&C revisions (3 in total) pretty much strip you of all your consumer protections and absolve them of any wrongdoing.
Taking them to court for breach of contract will probably not work, but small claims will. Under UK law you can cancel an internet purchase at anytime, up until 7 working days after you receive the item, so if they do ship you a box of Gridseeds you can send it back for a full refund. Assuming there's a company left to send it back to.
Thank you all for your replies, it's been very helpful.
All I have is what was posted in this thread recently from google cache.