Just a heads up for anyone thinking of doing the same.
I've just fitted an alarm with central locking. No big issues but when I got home the alarm wouldn't work. When I was about to activate it one of my children opened the door and so the snib didn't go down when the alarm went on (one door was locked whilst the other was still unlocked). Apparently this confused it and it stopped working.
To fix this I had to make sure both doors were locked or unlocked at the same time and then all was working again.
