I haven't seen this fault for a while but up until a couple of years ago I was still getting these changed for free at the Vauxhall dealer on 2.2 Vectra, Signum and Zafira models. I think it was after Watchdog investigating the sudden cutting out problem and how it could cause an accident. The last one I took in was a 2005 Vectra Elite and that was around November 2011. There was a recall/field remedy number I used to quote from TIS that ensured the work was put through.
Might be worth seeing if they will still honour the extended warranty on the regulator. They would never just supply the part to me on an exchange basis but would always want to do the job themselves which may be a pain depending on how far the dealership is and how quickly they can book it in. However you could always send the customer to them.
I also noticed that everyone I had changed would return with 1 male torx head bolt and 1 female. If yours has 2 odd bolts it may have been changed already.

Liam