well I have an update and some interesting news / observations of sorts.
I haven't found my meter yet so haven't done any measuring, but it is obvious that something has been draining the battery, I have not driven the car since sunday, and today (thursday) again the old dear did not start, with a flat battery. I attached a trickle charger, and left it for a couple of hours. When I went out in the evening (after dark) to check I had a walk around the car and noticed that one of the lights on the rear left side (red looks like the brake light) was faintly on. I opened the boot - no light. I opened the driver door to check indicators headlights handbrake, - nothing out of sorts. Closed door went back, rear light was off. Went back out after about half an hour, and the light was on again (still trickle charging on the battery). Looks like this is what has been draining the battery. I don't know why this is happening, it may be a wrongly connected cable to the light unit. I don't know why this would have suddenly happened. Any ideas? Can anyone point me to some wiring info for the rear light unit so I can check that it has been done properly?
I took a photo but don't seem to be able to create a gallery to upload the picture. Basically, in the rear left group of lights it is the red light furthest out from the centre.
Any ideas / help advice greatly appreciated.