That's the one! The old man equivalent of having to give it an extra shake before popping it back in
Successful session with VCDS, done!!
Teardrop/Extra shake wipers enabled.
Auto lock above 15kph and unlock on key removal, enabled.
DRL's off when handbrake is on, enabled.
Need sweep on startup, enabled.
Wheel size, set to a perfect reading on the odometer, and the speedometer is now 1/2mph greater than GPS speed at 50mph, and 2mph out at 70mph (68mph GPS speed. MPG is also now showing correctly, 40-45mpg sitting at 65mph for a minute on the instant readout.
I initially used the number 1 coding setting as this matched my tyre size (245/65R17 so 2357mm and 2355mm in the coding), but this gave ACC errors above 50mph, and the DSG box when downshifting for extra oomph was jerking really badly. I also found an error code which said "Unplausible/Unfathomable/Impossible (or words to that effect) reading from ABS sensor" so I guessed it was above what it could read and so the system was getting in a tiz. The odometer was also over reading, a 4.7 mile run was showing as 5 miles on the odometer.
Took it down a setting and it's now absolutely perfect, odometer reading exactly right and speedo a mph or 2 above GPS.
Sorted!!!
I may have a further delve and see what other options I can enable... Alice down the rabbit hole, this could be!
Edit: also just enabled the DRL's turning off when the indicator is on, and enabled the option to choose the default distance for the ACC which was missed when mine was added. I pretty much always use the closest setting, I can now pick that so it starts at that rather than the middle one!