when it comes to alarm/immob installs. i do it all my self as ive some of the "proffesional" work done by some installers.
e.g 1: my bros laser done though the insurance company, the assholes wired the immob to the starter motor, but his drive way is on a slope so i just do a rolling start, and the car starts.
e.g 2: mums old corsair (voted 1 of the worst cars of the 90's for good reason) also had a shit job done. immob was wired dierctly to the wiring on the starter switch, so when the immob shat it self i undid a couple of screwws, shorted the cut wires, and taped them up!
When i done the alarm on my car i had the main loom apart and wired the alarm/immob loob directly to it (loom sits under dash) then taped the whole lot back up, so all you saw when you pulled the dash out was a bunch of black wires going into the main loom.
a lot of work, but its worth it.
steve