As most people who track regularly would say, if you cant afford to walk away from your car, don't take it on a track.
TT is not something I have done, or plan to do in my M2. I actually get track insurance every time I go out since I do have a payment on my car. However, that doesn't cover any type of "racing" or "time trials" explicitly.
I'd say, if you're worried about it, its probably time to think about an (inexpensive) dedicated track car that you do not mind rubbing paint in, because its bound to happen sooner or later.