joeski

The common part of the linkage that drops off once the joint is worn is relatively cheap, did mine a few months ago, think it was £6. It happened about 2 years ago and I got some linkage clips off ebay that worked well and lasted 18 months, I'm guessing I'll get longer from the new linkage arm though. Really easy job, there are videos on youtube to help you.

I had a similar issue last year, it turned out to be a faulty microswitch in one of the door locks telling the car that a door was open when it wasn't. It's easy to diagnose, just look through back window when the alarm is triggered and see if the door open light on the dash is on.