I heard back from VW and have confirmation on a few points that might be of interest:
Front diff lock needs oil changing at 3 years in perpetuity. The front differential lock of the Golf GTI “Performance” is also fitted with a multiplate clutch which corresponds to the Haldex coupling and I suspect this will also apply to my TCR.
The other items are obvious - Spark Plugs (4 years), Air Filter (6 years), Pollen Filter (2 years), Brake Fluid (3, 5, 7 years).
There are two types of pollen filter in the parts catalogue - the hypoallergenic is more expensive. I replaced mine recently and did a decontamination of the aircon. Irritatingly, they sell you the can of antibacterial/fungicidal spray but not the clip on applicator with extended hose to go down the vents. Got one off e-bay. If anyone needs part numbers on any of the above, happy to look them up.