Reconnect the horn for the alarm (it's in the boot behind the trim panel drivers side (o/s)), then press the bonnet switch on /off a few times till you get a 'pip' this puts the Perimeter alarm in 'self test' mode - then go round all the doors open/close should get a 'pip' do the same with key barrel switches, should get a 'pip' when locking AND unlocking and the bonnet/rear hatch.

If any of them don't 'pip' you have an ajar or lock switch fault.

Saves stripping out doors/panels you don't need to.