As for the Alarms, i self installed (im a electrician and used to do alarms/stereo work on the side), my alarm, its a Balck-Widow...
If i was to get another alarm, i would buy the RA from Rhino, with an internal Siren, and ultrasonics.
The thing about 306's is that you can grab the top corner of the passengers door window frame and just reef it out from the car. You only need to move it out 5-10mm and you can thread a long steel rod to the other side and flick open the doors, hence the need for Ultrasonic detectors...
One thing to look out for, is the Central locking control box is under the rear seat, but its not a logical item and the installer must know what he is doing... its best to try and get a reputable instaler and perform the work at their premise. Also invest in an internal siren.. Also look into the imobilser side of thigs and make sure they don;t just work on the ignition cicuit, the fuel pump is S/w on via relay, its bestto isolate this with reliable external relays, as it might kill the onboard relays on the alarm, depending on the brand and who puts it in... good luck Xq