Q7 Battery Drain - Before I sell 'as is' :-/

After 10years and 187,000 miles of trouble free motoring I'm at the point of selling my 2006 3.0 S-Line Q7 'as is' with a battery drain issue, but I'm looking for some advice before I do...

Is there anything simple I can do/should check?

The car has a new battery (replaced earlier this year 2018, under warranty) and the alternator was replaced this time last year 2017.

But the battery has run flat on me twice since... so flat you couldn't even 'pop the locks!'

(It starts and runs fine following a 'jump start')

But I've had enough... as I don't feel I can rely on it like I always have.
Should I advertise on Auto Trader?, or is it best to use E-Bay (with a relatively low 'reserve price' of around £3500)

Hmm, Q7, electronics problem, simple solution, nahhhh! :1zhelp: Who has looked at it, Audi or a VAG specialist?

Yes, nothing's ever simple it seems.... so VAG specialist, as I didn't fancy the Audi £180+VAT 'initial assessment' fee i.e. £200+ to work out what they were going to do, and before they started to do anything!!
VAG specialist hasn't told me anything I didn't know already, i.e.. that the MMI unit was 'off line' - go figure! that;s why the screen''s blank and won't pass 'go' when you re-boot it - doh :-/

Even very good mechanics struggle when it comes to even the most basic automotive electrics, many seem to lock up in blind fear at the sight of a couple of wires, never mind hundreds and nearly everyone I have ever comes across does not know how to read a post 1973 style VAG wiring diagram, even some really good experienced VAG chaps; one who is a friend of mine looks at a VAG wiring diagram as if it is written in some alien langue, personally I like to print out the systems diagrams for something I am working on, crop and cello tape them together to form a scroll and then sit in bed studding them, but then again my wife says that is a bit odd. You need to start by getting full access to the battery which is easier with the seat out. Flick the door catch over so that the systems think the door is closed. Disconnect the earth terminal and connect it to a multi-meter that can cope with a peak load of 20a and upto 10a constant drain and connect the other lead to the battery earth post. Arm the alarm and allow the systems to settle for about 5 minutes so you can see the parasitic drain, this needs to be less than .1amp to be able to hold enough charge to allow access and starting after sitting idle for at least 20 days. If you see an excessive drain you have to start working out which circuit is at fault by disconnecting the (upto) five screw down and five push in fuses on the under seat electrics box (known as SD or fuse box D) one at a time until you see a current drop, then using the vehicles current flow diagram you can see which circuit this is and then go to its appropriate remote fuse board, SB, SC or SF and remove each one of the upto 144 fuses one at a time until you identify the culprit and the knowing that fuse identification you can again use the current flow diagram to see which device this is. If there is ANYTHING no original on the circuits such as car phone kit or whatever, this will add to the complication and is likely to be the cause of the problem anyway.

I don't know why this was closed, bit odd so I have reopened it.