Aftermarket car alarms

Does anyone know how much a fairly decent car alarm would cost + fitting for my vivaro van? I'm just getting more and more paranoid about it getting broken into with all my tools in it!

Any help would be great
 
Have you thought of a van vault? Sentri do some good ones and even if it gets broken into its a further hassle, with an alarm it will go off once they are in, but they can still grab a handful of stuff and leg it. With the sentri box fitted and an alarm, they will break in, alarm sounds and they normally leave empty handed
 
my dad paid £250 for a clifford system fitted to his Sprinter. He went for a couple of sensors and it works very well, the guy even came and installed it on our drive way, so i think we got a good deal!