Well I'd rather not have to replace the stereo again due to a thieving scumbag, so it would be worth it. It would also hopefully put my insurance down a bit. Mr T do an alarm that will interface with the Aygo, it includes sensors in the door pillars to detect movement inside the car and a siren mounted inside car very loud, this goes off together with the car horn, it has its own back up power. got its own fob as well. The price? £350 ish fitted, so you can get cheaper away from Mr T, but I got one fitted when I got the car. I'll call my local dealer and see if they can get it fitted. I understand it mightn't put my insurance down much, but I would rather not lose another stereo. I have started taking the faceplate off with me when I am not in the car and leaving the glovebox down to show it isn't in there, ofcourse this probably wont stop somone smashing the window.