Yeah, its a pretty minor saving to be sure, but you can't expect hundreds of pounds a year saving, or the company would just fit you an alarm for free!!!
For me its all about peace of mind - whether the insurance company requested it or not, I would always fit the best security I could, as I know I work damn hard to buy and keep my cars on the road, and I'll be f*cked sideways before some thieving scum is gonna take them from me.
Take Tobz's example - he has been on a quest for, what, a year to find his perfect Mk2? Imagine how gutted he would be if that disappeared - its a year wasted, and he needs to go back to square one and start again - that peace of mind has to be worth a few hundred quid alone!!!