As said, yesterday morning the siren was making really wied noises, a bit like dial-up internet or a fax machine. It wasn't the alarm as there were no lights flashing. So I disconnected battery which made it tick every 2 seconds or so while i took off the wing and removed the siren by unplugging it from its wire.
Are there any repercussions for doing this apart from no longer waking up the neighbours at 6 in the morning!