I had quite the opposite experience with an Accident Management company a few years ago resulting from similar circumstances.
I was down in Ashford visiting family, when a hotel delivery van smacked into my S-Max in a hotel car park. I wasn't in the car at the time. The driver admitted fault immediately, and gave contact details of his bosses. I passed all this info on to my insurer (Marker Study - Livinstone Warman) who appointed an AM company who were based close to me.
After a 10 minute phone call with them to discuss my needs regarding repairs and replacement vehicle I was quite encouraged by their ability. They liased with my insurer throughout and contacted me within 7 days (by text and a phone call) to let me know that other party had accepted full liability. They booked my car into my preferred repairer within the town (already on their list of approved garages as it happens).
They made sure of what my needs where from a replacement vehicle during the period mine was in the garage, and called me again with a choice of a few vehicles for me to choose from (ended up with a VW Sharan with about 150 miles on it).
No claims weren't effected, and all I paid was my £150 excess.
So yeah, I guess like everything in life, some are good and some bad. :shrugs: