Your facts are incorrect, Westie.
Concorde components were made at the relevant manufacturing site. However, there were 2 productions lines, one at Aerospatiale's Toulouse (France) site and the other at BAC's Filton (UK) site.
There were 20 Concordes, built as follows:
Prototype F-WTSS was built at Toulouse, prototype G-BSST at Filton.
Pre-production F-WTSA, Toulouse, pre-production G-AXDN, Filton.
Development F-WTSB, Toulouse, development G-BBDG, Filton
Air France aircraft F-BTSC, F-BVFA, F-BVFB, F-BVFC, F-BVFD, F-BTSD and F-BVFF at Toulouse.
British Airways aircraft, G-BOAC, G-BOAA, G-BOAB, G-BOAD, G-BOAE, G-BOAG and G-BOAF at Filton.
Anglo-French - half were built and test-flown in France, half were built and test-flown in the UK.