Hi Managed to get the wheel arch liner off to get at the alarm siren and thought I'd share what I found: Here's the siren - looking pretty clean and tidy: Used a hacksaw to open it up as nothing else seemed to work. So a few minutes with the saw and not so pretty inside: I taped up the connector and put the case/holder back in the car. New siren ordered so hopefully that will get it all working properly again. I had to buy a Torx security bit set and just for reference, it was the T40 bit that I needed to undo the Torx bolt. Feel very productive! Let's hope the new one goes in OK and works.