Just some background info from "The Bomber Command War Diaries":
557 aircraft took part; including 93 Stirlings. 35 aircraft lost; including 11 Stirlings. Post-war British Bombing Survey Unit estimated that the raid destroyed 64% of Mulheim.
George's service records might still be available to next of kin (cost £30 unless widow) from RAF PMA, RAF Innsworth, Gloucester GL3 1EZ; my father recently bought his brother's record. Not a great deal left but interesting to see where he was posted etc.
Nanny Jan