thanks for that - I will take a look tomorrow under that panel.
The reason for wanting to not use the cigarette lighter is that it looks a little unsightly with the wire trailing across the top of the shifter area and under the steering wheel.
Also, the only reason I wanted consant power was because the wiring diagram & instructions for the detector indicate that it should be connected in that way. I am sure that if I just hooked up the switched then it would be fine, but given that where you find one you tend to find the other I thought I may as well do it 'by the book'
thanks for your help