Just as a suggestion.
Before starting work on removing the seat belt reel, pack out and cover the area to the left or right of the fuel tank (depending which belt you are working on) with a cloth so that any spanners or fittings that get dropped don't disappear under the road spring. Otherwise it is a fishing expedition with a magnetic probe.
It is best to unscrew the vertical rear panel so you can get a hand onto the reel from inside the car, this helps once the bolt is removed and you are maneuvering the reel out, and feeding the belt and fittings through the slot in the fixing bracket. Apart from the nails in the carpet, and self tappers in the metal panel, there is also a bolt through to the cyclops light to be removed. I didn't remove the whole of the panel, just wedged it open at the top so I could get my hand in.
Getting the fixing bolt back in the reel when fitting the replacement is a PITA due to available height being less than height of the bolt - I angled it in using a pair of locking forceps
Finally, keep calm, it does come out, and goes in, just needs a lot of patience
