Aside from the coolant leaks there's nothing major in any of that, VD.
Apart from brake pads/discs and tyres I haven't yet experienced any of those issues in my MKIII Octy but have tackled a couple (as below) on the MKII. Nether the MKII nor the MKIII have adblue but I did come accross a known issue with VAGs that use adblue whereby it kills some component associated with the EGR valve and incorrectly self-diagnoses a DPF fault.
From the MKII Service Record:
19/08/2020 306,520 Timing Belt Kit, Water Pump, Clutch Master Cylinder €400.00 Aiden (supply & fit)
29/12/2020 315,221 Altenator €140.00 Euro Car Parts NI
13/08/2021 330,119 Battery €104.00 EBC Cabra
I don't know how much of the €400 on line 1 was for the clutch master cylinder supply & fit bit I'm guessing the timing belt / water pump kit accounts for the majority... and the battery isn't of the AGM / Start-Stop type. I did price that type for the MKIII a while back (the start-stop function has been a rarity since COVID '19 anall) and I think it was c.€200-220 from EBC, probably a bit cheaper up in the United Kingdom of Great Britain and Northern Ireland.
Front tyres tend to last c.50,000 kilos on both of the above Octys... that's for the run of the mill (non seasonal) now €75 ones from Collin or Keit Duffy.
Brake pads would be in the region of €15 (rear) or €22 (front). I generally change them every 40-50,000 kilos and use one set of discs for every 3 sets of pads at a cost in the region of €30-60 per pair depending on source.
