Car crash - what to do?!

Hi all, Vaguely copied from a post I sent to legal advice UK but my guess is they’ll say it isn’t legal advice I need… I’m freshly off a car crash. My very first after 10 years of driving. To cut it short, a van decided to go into my lane on the motorway and I had absolutely no chance of slowing down I’ve called the AA as this was the highway man’s recommendation. I’m currently sat at a service station, and just wanted to know my legal requirements on this one as I’ve never come close to this sort of thing before! The AA have offered to use a brand called “AX” to effectively come and see the car, see what it would have been worth, and give me the money for that. All skirting the insurers. Obviously great on the one hand, keeps it off my excess and claims etc. But surely there’s a catch? I’m surely legally obligated to use my insurer to chase down any monies owed? The next bit is I’m not going to be in the country again until Thursday, so not an awful lot is going to be done until then anyway!