It happened again this morning!!

They are really nice people and I certainly don't want to fall out with them - it's just this one thing which they can't seem to deal with. I think I may just put a sign on the car with the word "alarm" in big black letters!

That is without a doubt the most annoying thing to be disturbed at that time of the morning .. can you report this to a council officer or the police?
It is an offence to make undue noise any time between 11pm and 7am .. at least it's worth just giving them a ring to see how things stand even if it's after 7 that still doesn't give him the right to continually do that.
All the best to you!

If it were my car annoying the neighbours I think I'd be tempted to disable the alarm.

We considered, in our most annoyed moments, parking our alarming car at the top of the hill that runs straight down to the loch and taking the handbrake off!

Go out at 1am and shake his car. When he comes out to turn off the alarm, apologise and say you were half asleep. Repeat hourly until he gets the message :-)

That is what puzzled me Baggs. I thought unlocking the car would switch off the alarm but apparently in this case it doesn't.

If he's using the proper car unlocker, it's puzzling that the alarm sounds when he opens the door. Perhaps his key is faulty. We have this problem but if the driver opens the driver's door (and nobody touches any of the others!) and gives the ignition a half turn and back straight away the alarm doesn't sound. It's booked to be fixed at some point but the local mechanics are swamped with more essential work at the moment.

We had a faulty alarm in a car we had some years ago. It kept going off randomly. Once when we were staying in a small village at a youth hostel in the pennines it kept going off. Eventually, MrB drove it into the middle of nowhere and slept in it so that he could stop it straight away if it started again. Fortunately there was a warm sleeping bag in the car. I don't think he slept all that well but the car behaved the next day while we went to a family gathering.

All you can do is think that if his alarm went off because his car was actually being stolen, nobody would take much notice.. the car that cried wolf!
Its horrible, being woken earlier than you needed or wanted to be.