Aside from the markings, how accurate does the Lancaster represent those used in filming?
I would expect they had some non-wartime equipment or aerials since they were still active RAF aircraft?
The aircraft carried treaded tyres,
0.5 twin calibre guns in rear turret,
new ASI aerial,
larger rear canopy astro-dome
Squadron codes slightly larger than wartime sizes
and even the camouflage markings were simply Brown painted over the standard BC Grey used at the time.
The Lancasters used were brought out of storage for the filming