Id look at the accenta control panel, honeywell or optex dual tech sensors and a sounder of your preference. The ag6 is a good budget option.
http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=1010
http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=1676
http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=1973