Well thought I’d update this thread, as everyone was so helpful. So the car is back from Audi, the Toyota garage I bought it from had the warranty work of heater matrix and defrost flap motor approved and I actually haven’t checked the coolant level which I’ll do in the morning but the drivers side heating is fully fixed and I’m enjoying the car again!
£1600 in total, labour was £900, HM £250, flap motor around £100 and then flush £100, the rest VAT.
Fingers crossed that’s it for that issue now. Will post a photo when I can too, best when the suns out!!