I have found this!
Tells me where the alarm is on my C30
http://accessories.volvocars.com/en-no/C30/InstallationInstruction/Document/VCC-298068-1/2007/1.6D/Manual/default/C30%202007
and tells me how to replace it.
Not had chance to try out the instructions yet.
If I manage to fix it I will put up ...

My 2007 C30 has the message "Alarm system service required" Displayed.
I have seen lots of fixes for this on other Volvos on various sites.

Can anyone help me out by telling me where the siren module is located?

I have looked inside the wheel arch cover of the Front RHS but its not there.
The ...