Hi here is a link to a manual for your alarm:
www.electrical-services.com/images/PDF/Vertas%208%20user%20guide.pdf
I assume you have a sensor en route to the panel, this sensor needs to be changed from 'Guard' to Entry/exit or Double knock. This will enable you to have more time to reach the panel. You can change the zone type for each PIR sensor in your home to meet your needs. See page 23 of the manual. I inherited my alarm with my house and have been able to re-programme it without an expensive engineer.
Helen, June 2010