Just in case anyone has followed this, I found a load of documents about my Great Uncle. This is how he died, according to a hand-written letter to hi mother: "On that date my squadron was fairly heavily bombed, and a direct hit was scored on a supply vehicle of which your son was the driver. He and two companions who were sleeping near to him were killed instantly." I'm still waiting for service records for my grandfather. Thanks to everyone again who's helped me.