Markings on Aircraft

Did anyone notice the painted out military registration markings on the Avro Yorks lower wing(later post war markings). If you rewind back to when they board the aircraft in England the markings are seen and not painted out, but when it lands at Gibraltar you then notice that they have been hastily painted over with what appears to be white paint on a natural metal surface. I think someone must have noticed this after the first scene was already shot or it could be two different aircraft in the two different filming locations.But I cant understand why the job looks rushed and unprofessional ( a bit more research I think).
Also in the Gribaltor airfield scene a four engine aircraft can be seen in the background, at first you might think its a Lancaster bomber,but its not,but it is a direct descendant of the "Lanc" the aircraft in question is from the same company the Avro Shackleton MR2 maritime patrol aircraft.
Now the "Shack" didnt have its first flight until Mar 1949 and into service in 1951 so to late for service in WWII.
I guess its being in shot would be as set dressing and to the untrained eye wouldnt be recognised.