Paul, the small switch on the door pillar is the switch for the anti-towing part of the alarm. If your car has to be towed or transported, you need to use the switch first to stop it screaming it's alarm off
A UK car will be 'declared new at first registration' on your V5C. An import has slightly different terminology, if I recall correctly. Besides, a phone call to the previous registered keeper never goes amiss, you can find out a lot about a potential purchase.