Have a look at the optima panels, be wary of the environment for movement detectors, you may be better with door contacts for volume add a masterblaster to it.
https://www.securitywarehouse.co.uk/catalog/ade-honeywell-optima-compact-gen4-p-866.html
https://www.securitywarehouse.co.uk/catalog/klaxon-127db-240v-high-output-master-blaster-siren-12v-relay-p-1432.html