renault scenic uch pack broken. how do i fix it?

i have a T reg Renault scenic, i had problems where by the car wouldn't start, it turned out that the immobiliser needed reprogramming. However a second fault showed on the diagnostics, replace UCH Pack. Renault are going to charge me £450 on top of the £200 i just paid is it worth it. How long will the car run whilst it has a dodgy UCH Pack.

john
December 2009