well at least your safe mate with no injuries, sounds terrible but the car can be replaced, even if it is at your cost, but your life cant at any cost.
do you have any pics of the car mate? did you have the reflex pack fitted?
did the police come out? it may be worth contacting the police if there are cameras fitted on the m25 it may of been recoreded on cctv. just an idea mate which may help. let me know how you get on.