Just found your thread!
I was in that area a few hours previously and the weather was pants. Sc from 2000 down to sea fog. I bottomed out at 50 ft looking for a surface contact without seeing the sea. Al was flying with John Eyton-Jones and went to investigate a "surface contact" and they were not seen again.
Possibilities:
Shot down by "surface contact". V unlikely and never claimed.
Mid-air collision in ****e cloud. Possible.
Both flew into sea in ****e vis. Also possible.
Take your pick. Most unfortunate loss of two top blokes.