[Larry]

According to Bomber Command Losses book the crew are listed as you have listed them in accordance to their role, so S/Ldr Wood was the Pilot, Grealy was the Observer, and the remaining two would have been Wireless Operator / Air Gunners.

Even at this time January 1942, it was still possible for an Observer to be a Pilot who acted as the Observer, but probably not in this case.

I imagine you have the reason for the crash as being hit by Flak