There is a main live cable junction below the expansion bottle. Bit tricky to see, but connects directly to the battery. If (as it would appear) you have not fitted the boot lock correctly, the boot light might have been on all the time.
This sounds like a brilliantly simple and plausible explanation as to what may have happened !
Heres an update. Right now I dont have a car for tomorrow, and am really at a loss with all this, but here's the latest :-
I downloaded and checked through the workshop manuals (1000+ pages total), and on page 181 of 665 in total, of the "repair instructions volume 3", section 55-11, page 3, it specifically states that the cigar-lighter IS connected to the battery at all times, irrelevant of ignition key position etc.
So, with that in mind, I then connected a 12v 5amp max PSU via cigar socket, and set current limit low, just to see what would happen. IE, would it have a huge current inrush ? would the car show some signs of life ? etc I didn’t want to just connect a battery and end up melting something.
When I connected the PSU something did came to life under the dash Board / instrument area, and I could hear a relay or something clicking at 1 hz intervals, but this would trigger a current drain just in excess of what the PSU could supply … and it would immediately limit the current and drop the volts, and the car would cycle like this with each 1hz click.
I figured I might as well hook up a spare 12v battery via the cigar lighter. Turns out I had left the key in the ignition in the on position and all of a sudden the wipers alone came to life due to the WS lever also being one stop down from off. But nothing else happened, no other combination of buttons, keys, etc, would do anything else. I turned the wipers to off. Still everything was dead (everything means no horn, interior light, radio, boot release, nothing).
I then disconnected the battery and inserted a mutli-meter in line with the battery connection (current range set to 25amps max), and a 2nd multi-meter across the battery to monitor any voltage variation. I figured if there was signs of life then these two should be more than enough to see if any horns, lights etc would work, and monitor what would happen if I tried enabling the ignition.
But this time - nothing at all. 13v is going in with no variation and zero current being used, and there is no change to voltage or current no matter what I do with the ignition key, or any buttons / lights / horn / radio, nothing. I tried to ensure the cigar light connector was as firmly planted as possible, but no change.
What I don’t understand is that if the cigar socket is directly connected to the battery, and I hook up an external battery, how come there is now zero current draw ?!
So I am a bit perplexed as to what is happening.
If the cars battery had been totally flattened by something (possibly the boot light due to boot lock fault as mentioned by FoxTrotOscar), then is it possible the cars ECU has somehow lost its settings, and will now only respond if the special code key is used ?
Surely even with the ignition off, and the key out, something should still work and drain some current ... like the boot lid light if that was at fault to start with ?
I might try and find a more reliable / definite connection into a direct cable back to the battery.
It would help if I could just open the boot … right now I am thinking about drilling out the damn boot badge out trying not to damage the paint work But I am not even sure this will allow me to unhook the lock.
Appologies for big post, but I'm really stumped on this one ….