Primal, i dont know how this opinion fairs with other 'responsible' motorists out there but unless you do something crazy to your car like get a turbo i wouldnt bother telling 'big brother' anything about your car.
All i have done to my new Micra now is a K&N induction kit and some Nissan Micra alloys, but cos they aint standard, i wouldnt expect jack in the event of a claim. Sure if your cars worth over 5k tell your insurer about that powerflow exhaust etc. etc. but i wouldnt otherwise.
For example if you ran into a tree (write off) in your fully comp. Micra and you had a custom exhaust, they wouldnt pay up if you didnt tell them. If you did tell them though, and claimed, you would be looking at a higher premium in the first place, a claim to ruin your clean record ('protected no claims' is a fraud cos you still pay more), and a lousy payout for what your car is worth.
Anyway sorry what i was gonna say is you really have to tell your insurer everything about your car if you wanna get that discount for having a proper alarm. And it will cost a bomb to get a 'pro' to fit it.
If it was me i would get one between 50-100 online ebay etc. fit it yourself if you can, if not it wont cost much for a mechanic to. One with a shock sensor and makes lots of noise! They are a big deterrant! Ive been woken up in the past by just the sensor warning screech (dont know whether it was chavs peeking at it or the wind!)
Lol hope this helps. (basically dont get screwed)