Car has been in to VW this morning. The initial diagnostic confirmed the fault code, but they require another two hours to fully determine what's wrong, quoting £156 per hour of labour..!
Spoken to a local independant this morning to carry out the further investigation. They said it's not uncommon for the mechatronics unit controlling the pump to have issues for MY17 and 18 cars, but was fixed for MY19. The two options are likely to be replace the pump of course, or it can be sent away to be fixed, which should result in the fault never reoccurring.
Still unsure whether a replacement pump would be covered by the warranty given that the diff service has never been carried out. What's interesting is that the dealer I bought the car from serviced the car just before I bought it, but they didn't service the diff depiste it being overdue. I wonder if I have grounds to raise it with them, as if they'd serviced it the fault may never have appeared..? Anyone had any experience with this sort of thing?