I was in the same sticky position once, you realy have to put your foot down with the insurance company.
The garage use second hand parts and "sperious" (think thats right) parts to fix my golf gt tdi. I waited firstly 8 weeks to get the car back the paint job was a mess, the enging bay was shot to hell with cut and joined wires everywhere. The wing they used was from another crashed golf and it was red, my car was black, Looked like Fu*k all.
I called everyday untill they sent out there head assessor, he concluded the car needed to be put right. Another 4 weeks latter car was back to me and was no better that the last time.
Finaly, after 5 months of rented cars and running about my golf was put right by another garage, of my choice.
So my advice GET ON THE BALL AND DON'T TAKE IT!!!