Hi
Ive just put one on Dads..
The plastic "mount" that joins the mirror to the electric mechanism..was about £4 on net and about £5 from LR .Slides on the back of the glass and pushes on the motor mechanism (Providing you still have the broken glass to fit back!) If so,i went for a stick on mirror Sticks over broken glass,and heater still works through it) for £18 off net...About £15 in Halfords but 2 week wait!!!!..
If your glass has gone,a new glass is £40 out of LR if i remember right..
Hope sum help..
Cheers LTel