Personally, my advice would be don't deal too early - yes it's fab that Audi are replacing almost the full breaking system - which in itself i know is pleasing to know against the wear and tear of owners pads and discs - but remember, particularly those who have had the issue for months - and more importantly recorded at Audi UK - a service is a nice gesture, but if Audi said when you first experienced the problem, "here is £200 now go away for a few months" would you have been happy to persevere with the squeal for months?
For me you know the answer, but before I decided upon a full refund I had various other 'goodwill' negotiations. I do however appreciate the thought of a fix of this magnitude (assuming it works) is a form of compo in itself - in depreciation terms - as appose to a set of shims as the fix.
Just out of interest, I wonder what a dealership would charge for the cost of the fix parts and labour assuming it was a bill to a customer....I'd stray a guess at £6k??? And I ask this for a reason......
Why not collectively write to Mr Sander - quoting sale of goods act - and then suggest your collective offer of compromise......maybe suggest servicing for 3 years and extended 5 year warranty....or £5k off your next purchase on a £40k car in the next 2 years; or an R8 for a week; or at the very least a courtesy of explanation as to the reasoning behind this expense of fix......as they don't replace all these parts surely for purely an audible cosmetic fault?
...don't get me wrong, though for all my whining, the RS3 is by far the best car I have owned and made by replacement such a difficult choice but in the end an easy one ;-)