I've done the search and this seems to be a common problem.

My vRS alarm has now gone off twice, but the funny thing is it has only happened on the last 2 Monday nights both times around 10-15pm.

I've stayed at my girlfriends house on the last 2 Monday nights and park on a steepish drive with the car facing uphill. It's been cold both nights. Once the alarm is turned off then back on again all is well. (air vents set to foot level).

Maybe it's the change in temperature setting off the interior sensor?

The car is still under warranty so I'll ask Skoda to give it the once over and report back any findings.

Found my alarm goes odd times on my 2005 Fabia VRS. I found on this site that the tailgate sensor gets a bit sticky and triggers off alarm.

Open tail gate look down into tailgate locking mechanism (above spare wheel area) and you will see a large black round button.

With your thumb press down on this button and release several times, you might get lucky and stop problem. (Fingers crossed)