Hello Manu,
Firstly, I have removed the Audi dealer name a location you stated, since this is an open forum, and anyone can read it, so you don’t want to leave yourself open to legal challenge.
To answer your questions:-
The splitting and wear may just be marginal at the moment, so in effect perhaps they don’t need attention now. My recommendation would be get this car independently checked at a trusted local dealer, and follow their advice regarding whether to change at this time.
If they do need changing now, then I would renew both lower wishbones as complete units.
Have a look at the Parts in Motion (Exeter) website, input your reg. no. and that should come up with some alternative brands for you.
My recommendation would be to buy a reputable brand such as Febi or Lemforder, and I certainly would not buy on lowest price.
Price to fit? Ask your local garage to quote you for replacing both lower wishbones.
Could you please come back to us Manu and let us know how you get on.
Kind regards,
Gareth.