I used a similar service a few years ago. We'd already agreed a trade in sale on our old car, but two days before the exchange it got scratched in a car park, so I needed to get it sorted out.
Approaching the franchise holder direct with cash in my hand, it was plain that the business model depends on an inflated price for any work being paid for by an insurance company.
Paying the guy directly cost I think about 30 quid. It was only about fifteen minutes work but he polished out and touched up the scratch so it was all-but invisible, using specialist polishes and experience.
Worth it at that price but I would have been reluctant to pay the £100+ "list price."