Sounds like one of the door sensors, or the interior sensor above the drivers side door.

This does seem a very common fault with the mk2 ZS :slap:

I thought it might of been the drives door sensor but it has also happens when someone gets in the back first,I then thought it might be what you said the interior sensor so im now testing that theory out ive now locked the car with the keys so i shall see what happens.

The interior sensor has allready been replaced about 5years ago because the alarm would go off at any time day or night.

I took that off for a min when the alarm started going crazy I've put it back on and nothing so far wish I had tools to at least take the noise box off so it stopped making the noise

Managed get the sounder unit out for the time being now my last paranoid question is the car won't use the horn for the alarm now will it???

No, the horn only sounds if you have miss-lock situation ie when lock the car remotely with a door or boot open.

Been there in the past. Once when I was dropping a date home to a quiet neighbourhood at night!

cool....they will still run also

managed get some piccys of the board as i ripped it apart and took the batteries off so it canna go off in the house lol

looks fine to me TBH but ill bash the piccys up

Maybe let it dry out more for a couple days and try again. I used a hairdryer. Also test that the internal battery is ok.

how wud i do that buddy??

Disconnect it, put a multimeter on it and measure the voltage.
Alternatively, connect it directly to the siren and see if it makes a racket!