If you're getting a hire car from an accident management company, get the cheapest one you can. Just in case you end up footing the bill (it does happen more often than you think), you could well regret getting the decision to spend £120 a day instead of £30 a day...
You do have a legal responsibility to mitigate your losses too, and whilst I'm sure everyone will shout me down and say that you shouldn't be deprived of a nice car when it's not your fault (which I agree with 100%), surely you can live with anything for a week whole the work is done. Plus, it's just as fun to drive something crap every now and then, I had some proper stinkers when I has some issues with the 911!
I also had a Merc C220D, which was a beautiful thing to drive and let me experience something I normally wouldn't consider.