I have to do the 3 button press to stop the alarm from going off top up or down. Is this likely to be the sensor module or something else?
Three button presses will switch of the motion detector, so it does look like your problem is with that unit. It is located between the two seats just under the storage bins - if you remove the centre console you will find it lurking at the back perhaps with a flap of carpet over it.
The motion detector has a sensitivity adjuster on it, so turn it right down and see if the problem stops. If it does gradually turn up! If you do this with the hood down, it is sensitive enough when waving your hand around inside the cabin sets it off.
Ive ordered one from a breaker but for the moment just unplugging the sensor resolves the problem of it going off. The doors still lock/ unlock and trigger if the boot and bonnet switches are opened.
Sounds like a fix!
Fitted the £6 ebay sensor and all works now :)..............now on to the timing cover oil leak, not going to be quite as easy.