Brian
Must have been a horrible morning for the 68th!!
I cannot add anything you already know, except perhaps that Jim Halley in the RAF MA100 - MZ999 states that MM643 was shot down by a Bf 109 while Norman Franks states as you do it was by a Me 410. Since it surely happened during the day, a Me 410 sounds a bit strange doesn't it?
IF MM920 IS the right Beau, it survived it's shoot down as stated in my first e-mail.
The loss of MM656 sounds strange. Again according to Halley, this was a Mossie sold to Sweden....
Cheers
Stig