It's been clocked!
I remember a thread about 6 months ago for a cheapish S8 with identical, odd, spec ACC, lane change etc... but was high miles (196k). If I can find that thread I'll edit this post.
Edit
http://forum.a8parts.co.uk/showthread.php?t=10692
No pictures but note what Olly said in that thread
"Also the exhaust tips are sticking out a bit further than normal?"
Anyhow, this looks like the same car but with a haircut in the odo reading
Advert says 147k, DVLA says 196k