I think i spy one to the right of shot when Barnes Wallis is walking to the car after talking Mutt Summers in front of the DH Mosquito (before the test at Reculver that finally works).
I'd find that extremely doubtful - the English Electric Canberra was at the design stage in late 1944 but the first Canberra didn't take to the air until May 1949, long after WWII had ended.
My father worked for English Electric, and I was thrilled to have a full-colour poster of the aircraft on my bedroom wall in the mid-1950's by which time it had established itself in substantial numbers.
I rather think you're missing the point the original poster was making. Since the film was released in 1955 it would not be altogether surprising to see post war aircraft on the airfields. To answer the original post, yes, I believe there was a Canberra in the distance during some of the shots. If you look carefully there are also some Lincolns and they didn't arrive until the war was over either!
Although the presence of the Lincolns would appear to be deliberate as they looked close enough to Lancasters from a distance to be used as `stand-ins`. The Lancasters in the film being the last three operational examples in use by the RAF at the time!
"Any plan that involves losing your hat is a BAD plan.""
Yes there was a Canberra in the film at that point, you can clearly see it through the rear side window of the car that Barnes Wallis gets into. It probally wasn't meant to be there when filming and was missed during final editing.