Making progress on your own there Jo
As said above, make-good at that burnt cable and tidy the rest without disturbing it too much, -even just a few little cable-ties would help. Make sure all existing connections are good tho, not just twisted and taped. Fold-over and tape any chopped off redundant wires.
Once this ropy bit is fixed you can forget about it. Hopefully.
(We still don't know how the damage occurred in the first place).
The jumbly mess at the steering column doesn't look too bad to re-route to the way it should be. There's a chance that brittle connectors may fall to bits with you when you unplug them but it has to be done. Discon battery.
Maybe best leave that till the switch-cam gubbins arrives?
Plenty to do.
A bit of trial & error with seat belt reel angle may solve that problem too.