Haynes Sierra manual the latest one (covers up to 1993) - £4 plus post (£3.50?)
Xena XA601 Garage Alarm, cost about £45, less than a year old take £20 plus post (£5?)
http://www.xenasecurity.com/product/pir/main/XASeries/XA601/page1/
The XENA XA601 passive infrared zone alarm is a standalone battery-powered motion detector that fits to the ceiling of your garage, home, caravan or business. Conveniently remote-control operated, the XA601 features a new updated four-part infrared sensor for increased sensitivity.
The siren is triggered if anyone moves into the security zone. A 15-second delay allows the user to enter the disarm code without triggering the siren. Once triggered, the siren sounds for 30 seconds before resetting.
Features:
• Infrared Beam
• 20ft.(6m) Range
• 135 dB Alarm
• Remote Control
• 360-Degree View
Battery:
4 x Alkaline C batteries
Battery life:
Approximately four months (based on five arm-and-disarm cycles per day, alarm activation four times per day).