As long as there are pics of the repair I don't think the price is bad at all. The £5k bill was probably for the full repair @ the bodyshop including paint etc.
Some cat C cars I have seen shouldn't even be recorded as D's and vice versa. Insurance companies with high value cars sometimes rate piles of scrap metal as cat D and they should be B- Break only.
The category depends on the assessor and the estimated garage repair bill which is sometimes over estimated for various reasons.
Wheels made me sick into my paper bin