Hi Paul,
The company NP Aerospace, or National Plastic had there own part numbers, 11431-011 for LH door and 11430-011 for RH. I believe the actually maker of the door locks was Widney UK Ltd, Plume Street, Aston, Birmingham, B6 7SA. They had their own part ref. no's, 76/52632-LH and 76/52633-RH. Worth contacting Widney if you are after a replacement as it is quite possibly an off the shelf lock for other application as well. The company are well known for vehicle sliding seat runners, sliding windows in buses and all manner of auto body parts.
regards, Richard