Zorst prob just fitted poorly. Bracket adjustment
Airbag. 98% nothing to worry about. Give the passenger connector a wiggle and perform the reset with the car key (takes less than a minute).
Clutch, discs and pads are prob the thickend of £1200 depending on brand but don't let that and a couple of sparkly bits make you pay over the odds. That's a sub 8k car for definite.......if it was absolutely immaculate it would struggle to fetch 8. Sounds like this one needs a little tlc to be that standard.