Rodger - looks like he was there in late 1943 - see attached link:-
Dambuster - Guy Gibson which was recorded in Canada and now available on CD.
Dambuster - Guy Gibson. Product code: TRD200897/CD. £10.95
A unique CD featuring an exclusive interview recording made in Canada in late 1943 with Wg Cdr Guy Gibson and, following the Dambusters March, 8 of Guy Gibson's favourite records are included - with additional comments from actor Richard Todd. Also includes an interview with 617 Squadron Lancaster crew who describe the attack on the Mohne dam.
I'm sure others will provide more specific dates. Reg probably flew with him!! (Probably was his instructor and taught him the trick about how to judge when you were 60 ft above water!!)
You may also be able to get hold of a copy of the book The Dambusters
This is an excellent biography of Guy Gibson of which the Dams Raid is only a very small part of the book. The book covers the life of Gibson from birth to death.The story of his unhappy childhood from a broken home, his tense and failing marriage,his relationship with his men, which wasn't alway the best,particularly the ground crew.His life wasn't easy but through his determination he was noticed and came to lead the raid that was to make his name.Some of the book covers his tour of Canada and America and his dabble with politics and selection as a Parliamentary Candidate.The story of the making of the Film "The Dambusters" starring Richard Todd was good, including the "Spooky" incident involving the dog that was to play the part of Gibsons dog.The final chapters involving the fatal crash,the theory of how it may have been caused,together with the legacy of Gibson makes for a very interesting read.