Did you check the new fuses?
Did you change the battery?
Have you had any works done recently, especially carpets being fitted?
Remove all the external sounder wires and mark or photograph the colours and where they go. Then trip the system or do a bell test and using the multimeter see if there is voltage present when triggered. If not its dead.
A new one isnt much these days, £40 ish.
Cooper still exist, but tech will not talk to you as you`re not a registered installer.
Alarm
November 2012