Complex sentence: Although the first 222 aircraft were built by Proctor at Luton most of the remaining aircraft were built by F. Hills & Sons of Trafford Park near Manchester, they built 812 Proctors of several marks between 1941 and 1945, assembling most of the aircraft at Barton Aerodrome.
Split into simpler sentences: Although the first 222 aircraft were built by Proctor at Luton, most of the remaining aircraft were built by F. Hills & Sons of Trafford Park near Manchester. They built 812 Proctors of several marks between 1941 and 1945, assembling most of the aircraft at Barton Aerodrome.