All sorted today. Found that at some point in the car's life that the support bar on the underside of the rear bench seat had 'squished' the cables leading to the yellow connector for the airbag igniter. The wires looked nibbled, but when I noticed that there was bits of the TESA tape stuck to the support bar I found the problem.
Cleaned back, reconnected, and all is well!! No airbag errors!
