Sorry, didn't see this thread - I was posting pics on a new thread late this morning and had to dash back to the beach again, summoned by my pager, and when I got back I finished what I'd started.
See http://www.ybw.com/forums/showthread.php?t=223841
Spot on, it has been reported a few times that sands were shifting prior to trinity house doing another survey after other yachts had been aground unexpectedly.