Well, car is at VW dealer right now, they confirmed it's the thermostat housing/coolant pump leaking which needs to be replaced, £1400
They also pointed out some heat spots on my front brake rotors, which they recommended replacing the rotors and pads, for £820, that is a lot for 2 brake pads and discs right? Rears possibly also need doing.
Think I will bite the bullet on the coolant pump, also needs front diff oil and brake fluid done which is about £270 between them but that's not too bad and they were last done 3.5 years ago. The brakes I will leave and maybe get done somewhere cheaper (or maybe even brave doing them myself).
So I'm looking at about £220 for the service + £1400 + £270 so about £1900 all in.
Not fun but I suppose it's not too bad considering I've had the car for 4.5 years now and this is the first real expense other than normal services etc. Cheaper than leasing at least
Kind of annoying to hear about how common this coolant pump leak is though, I've found a lot of people having the same issue online (and my friend had the same thing on his S3), there was even a class action in the US and they ended up offering an extended warranty on it for 8 years there, but no such luck here as far as I know.