Good going Wayne.
As for the seat belts, the MkIX version shown is the earlier 'Sutton' harness type, which utilised the grommet holes for overall adjustment, and a cotter pin through a metal cone as the fastener. Under tension, for example if pulling 'g', this could be difficult, if not impossible, to release in an emergency. Also, the 'Sutton' harness was made from natural-fibre canvas webbing, which had been know to fail in heavy crash landings. These were replaced by the later version shown, using a mix of natural and synthetic fibres, for strength, and a 'quick release' box fastener. This type was also fitted to late-production MkIXs and XVIs, and the MkXIV.
Note that most current flying examples of the Spit shown in 'walk around' shots, will be fitted with modern harnesses, due to safety regulations in the various countries.