S8 with gearbox woes. Code advice please.

[Bushido]

Yes, this is the s8 that people will be fed up reading about!
Used to belong to Ollie and is a gem - all aprt from its gearbox. Car has been off road a year now whilst trying to raise funds / abandon all hope and just call it a day.
As it was going up fro sale, I opted to get a fresh MOT to enable perspective buyers the security of knowing where everything else with the car lay. (must check if it passed! )
Quick recap. Car has 174k miles. Masses of history including gearbox oil. Driving out of a car park one day, put my foot on accelerator to pull away and the car just revved and sat stationary. Had NEVER had a sniff of an issue previously! Withy more revs, the car clonked in to gear, threw up all of the gear indicator lights on the dash and had locked in to top gear. It was limped home and used as little as possible thereafter until a replacement car was found.
Whilst away for MOT, my friendly mechanic managed to get it Vagcom read. It has thrown up these codes and information -

3 faults found -
17117 Gear ratio Monitoring
P0730 35-00 Incorrect gear ratio

18232 Pressure control valve 3 (N217)
P1824 35-10 Open or short to ground - intermittent

18227 - Pressure control valve 2 (N216)
P1819 35 - 10 Open to or short to ground - Intermittent

Of note, a specialist (and experienced s8) gearbox man condemned the box as showing all the typical signs of a clutch(?) at the very front of the box as being at fault. He was 100% sure that the almighty clonk when first taking up drive was all the evidence we needed. In fairness, the fella gave me over an hour of his time and was happy to show me on other disassembled boxes the problem he felt we had here.

Now we have the codes, does this shed any more light on the situation? All I would add is that the car has covered a couple of hundred miles whilst in this 'limp mode'. Whether this explains the incorrect gear ratio monitoring Im unsure?

All thoughts and experiences will be very much appreciated whilst we make some longer term decisions about the fate of the car.
Thanks as always for taking the time to read