Just a little note in addition to the other threads:
Your insurer/claims department must believe that you have a good case and relatively good chance of success as they wouldn't have given you a courtesy car; especially as TPFT. They usually only do this where their chance to recover the monies from the other party is 51%+ (unless you have paid an additional premium to guarantee a courtesy car without conditions etc.)
Shark, however, is right. You didn't stop, and YOU hit the OTHER party. If you can see someone doing a manoeuvre in a road, why could you not stop in time, or even at all!! You 'slowed a little'... quite frankly this isn't good enough and the right/wrongs of the other driver is irrelevant; I certainly wouldn't honour a claim or sanction a courtesy car if this information was given to me.