spimbolligan,
Ask him what else he flew. Nobody 'just' flew Hawks. it was a part of the fast jet training pipeline, so it is entirely possible that the Hawk was the LAST aircraft he flew in the RAF, if he was chopped at Valley or TWU.
Also, in the mid seventies it was also entirely possible for a GD(P) not to have been anywhere near Cranwell.
Also, you may want to have a quiet word in his ear about the consequences for him of a reference check revealing that his CV is less than truthful.