Colin,
I'm not honestly an expert on this subject, but my advice would be to try and get in touch with some of the people who are specialists in the history of the RAF during the war. In my case, I have received an enormous amount of assistance from an aviation history society in Brittany, which is where the plane went down. Apart from the headache of my having to write in French, which is very much my second language, they have been wonderfully helpful and we have found out all sorts of information which we did not know.
I started from knowing nothing but the type of plane, the date of my uncle's death and his service number, and the fact that the plane was on a mission to Brest when it disappeared. I found the names of the other crew members off the lost bomber website, and then got in touch with the people in Brittany, who have an enormous amount of specialist knowledge. I also borrowed several books about Bomber Command from the local library which gave me a good context to what I was researching. (I can give you the names of some I found helpful if you like.) My understanding is that there were a lot of Canadian squadrons, and that they actually formed a whole group in Bomber Command during the war.
I too have written away (yesterday) for my uncle's service record. (I realise this is actually the logical first step. but I had to get my father to sign the form as next of kin, so I am rather doing things out of order.) However, I did phone the RAF and had a very useful conversation with a woman who explained that there is not a huge amount of information on a lot of them. It tends to be things like contact details, next of kin, form type stuff, postings, training etc. There is nothing about missions on them apparently: I specifically asked this, because I did not want my elderly father to get gory information on a form about how he was killed. To get information about missions, you do have to get the Operations Records Books for the Squadron. As it was an RAF mission, I still think it quite possible that the National Archives would have it, otherwise you may have to go to Canada.
My cousin in the UK had my uncle's log book, which was useful, because it listed his successfully completed missions. (He died on his fifth op, which was pretty average. They did not have long life expectancies.) I am now in the process of getting the ORB information from the National Archives. My cousin did write to the RAF museum, and showed me the correspondence, but they were not awfully helpful. They did however, send her a photocopy from a standard reference work which cites all the Bomber Command losses of World War II. This also cites the crews of the lost planes. Also, they will certainly know the proper place for you to search if it is not in the UK.
Regards
Natalie
