What is the standard Cat1 alarm/immobiliser
fitted to a MY2000 Impreza Turbo in the UK?

I am importing a Dutch MY2000 spec UK car but it does not come with the Cat1 alarm/immob which I understand is usual for a UK supplier car. Am I correct is saying that this Cat1 system is also fitted by the dealer or dealers selected company?

I want to fit an alarm that usually fitted in the UK. I have a Toad Ai600, which I cannot fault, on my RS Turbo.

TIA, jon

Its a Sigma M30 i think.