My car is booked in for a service next week a the VW dealers in St. Albans. I asked them if they would check the diverter valve as it's quite a common issue to have leaks and what not in the MK5 GTI. But instead of hearing "yes of course", they said "sorry, we have never heard of a diverter valve, and neither has <MALE NAME HERE> who has worked with VW for over 20 years.
Why is there confusion about this?