S8 Heater issues

Good morning folks,

Poolcow here, quick intro as not a fan of just jumping in and asking for advice without saying hello first. Long time lurker ( joined in 2014 I think lol ) but not a regular poster. Bit of an Audi man having gone through a lot of the range between me and Mrs Poolcow we've had TT, A3 Quattro, and she now on an S1 and I'm A4, A6 Quattro, Q7, A7 Quattro TFSI and onto my latest and so far the best S8.

Struggling with what's next after the S8 tbh but liking the look of RSQ8, just a bit out of my price range when it does land lol

Anyway enough rambling to the point. I'm hoping somebody could help with an issue I have just had on my 2015 S8.

Given its brass monkeys my lovely heater has decided to only blow ice cold air out. Last nights journey home in a T-Shirt was very pleasant.....

I have had something similar with the A6 which was resolved by some advice from here I gleaned and hoping a resident expert can help out with the S8.

Its not been a gradual reduction of heat but sudden where's it all gone moment. Engine temp is fine and when it first happened I did the IT fix of switch it off and on again ( all car ) and it blew hot. Now today its freezing and wont come back despite on and offing it a few times.

Suspect it must be something electrical given the sudden nature of the fault but before I bend over at the dealer I like to know a little of what I'm about to be shafted on. Its 5 months out of Audi warranty but do have private warranty to fall back on but again forewarned is forearmed.

Any experts out there seen similar and proffer any sage advice please.

Many thanks in advance Daz ( aka Poolcow )