I finally sorted out my passenger door lock mechanism which wasn't triggering the interior lights or alarm. I bought a replacement for £18 and had just got to the point where I was going to extract the old mechanism having disconnected everything apart from the wiring plug and the door pin rod when BINGO my interior lights came on! I decided to stick with the old unit for now as the micro switches seem happy (scared) and the 'new' part is untested. This is a job best done by a right handed person with small hands (I'm left handed as you probably guessed).
Richard