Casper

I've almost bought a 1998 NIssan Micra privately from a couple who only live 2 miles from me and they said they would bring it to me, rather than me have to walk to get it. The couple are lovely and my friends know them well, they've had the car a year and their son learnt to drive in it, but now he wants something different, it's just passed it's mot, so, they bring the car round tonight, the lady stops it on the road to check she has the right address, and now the car wont start....every time she turns the key the alarm goes off.. Her and her husband try everything they can think but it wont start. We've had to push it up the drive just to get it off the road and they have gone home to return tomorrow for another look in the day and when it's warmer.. They have said that they understand if I now don't want the car... I'm wondering if it will need a diagnostic check to reprogram the immobiliser, or are they just doing something wrong? they say they have never used the alarm..