MB retail for that car is between £7-9,000. This suggests to me the damage was more than just a couple of panels requiring a respray. The A class has a sandwich floor and damage to this is expensive to repair. I'd want it to be checked properly, including full laser alignment, rather than go on some shiny new panels and paint.

I would be extremely wary . - for a lateish low mileage car to be written of as cat c it would usually need to have taken a knock hard enough to cause some suspension and chassis damage requiring a body jig. That's fine if an insurance approved bodyshop/main dealer is doing the work but how do you know the quality of the work is good ?. Or was the car written of after a minor bump because it was already a cat C car from a previous major accident ?.

Personally I only buy older cat d cars now for my own use and later high mileage cat d's and never anything on a cat c. And I would only buy a damaged car direct from a salvage yard so i know exactly how severe the damage is. , And then i would expect to keep the car for myself over several years until it's trade in value was low anyway

There is just too much scope for back street bodyshops to cut corners imho ..using roofing bolts, superglueing up air filter boxes, but welding on new chassis legs etc. the potential to bodge is massive, . Also check with your insurance company if they are happy to insure a cat c.