So, the final AAIB report is published. Its very short, here is the text:
Investigation into the accident to AS332L2 G-WNSB on 23rd August 2013
Cause: The aircraft crashed because it hit the sea, as a result of incipient vortex ring state.
Safety recommendation: Pilots should undergo increased training in the recognition of, and recovery from, vortex ring state
So now we know, and with a bit of extra sim time doing VRS training we will all be safe and it won't happen again. Phew, we can now go back to business as usual.