Hey Mule
Thanks for the idea, but I do think it would
WAY too much of a coincidence for it to be some other new/novel cause.
My lovely LE has only ever "let me down" once with the oil cooler/piping going on the M1 after 33000/5.5 years, and the OEM Clarion radio had not once been left on to deplete the battery.
Since my Sunday jumper-start and two 30 mile journeys, I've just tootled round town half a dozen times and Volts have remained at normal 11V on dash on start, and 13V when running and no hints of any starting problems.
So I'm reasonably sure that fitting the new radio had caused a sudden loss of juice that had only ever happened to me once before when the original battery was on its very last legs in the middle of a cold winter snap after 7.25 years (when £34 in Costco for a Bosch Silver 6PN came to my rescue).
The radio's UK distributor was adamant that to solve my battery drain problem I needed a 'switched' connection feeding their unit.
Anyway shall soon find out I guess as have fitted this afternoon a fresh Kenwood unit that's fully documented in the manual as wiring suited to permanent 12V supply, and confirmed by their UK support as such.
Nice thing about the Kenwood is that it's 'colour-coordinated' to the LE with a Titanium like surround, with black, and then relatively discrete Red illumination = made for the LE
I am 100% sure it was OFF when I put the car in the garage this evening. (My test meter was showing steady 12V on ISO A pins 4 & 7 before fitting BTW.)
Tho you are of course right it MIGHT be coincidence AND as I originally said while I was 99% sure I'd turned the Tevion OFF before parking up the car, it's just POSSIBLE I might not have. Anyway it's an issue to be alert to; if nothing else for Coupe'rs to decide if you DO want to change the std radio wiring to be ignition switched to avoid any chance of such battery drain while car is off.
Fingers crossed anyway, and jumper leads kept in the boot!
DT