Hi Callum, sorry to hear your having issues. I can't say I've seen it previously on here. I'm assuming you've taken your a3 to Audi?
It'll be interesting to see what the tests come back with. But if Audi do say that you need a new headlight (this is the worst case scenario) then I would argue there should be some factory good will applied as the headlights should not need replacing on a 64 plate. Unless your a3 has previously been involved in an accident and not repaired properly. (Again I'm just seeing the worst case scenario).
The adaptive lights are controlled by motors I believe and these can seize or fail, I'm sure.
Cheers
Steve