Golf Mk4/MkIV central locking problem - so annoying!?

Can anyone help me resolve the locking problems I've had for some time now. If I lock the doors, sometimes it doesn't lock all of them or likewise doesn't always unlock them all. Usually resolves itself if I relock & unlock. Worst thing of all tho is if the boot is open or any other door sometimes it takes it upon itself to lock, as the door is open this is usually followed by the alarm going off! Oh and not to forget the way it sometimes locks on its own - once I had just put the keys on the front seat, shut the door and yes you guessed it....had to then get the AA out to break it. Car is great otherwise but really getting annoyed now with the intermittent locking problems.