I would be interested if any of the membership have had a positive experience of having an engine reconditioned but not by a main dealer. My A6 has done 221K miles, runs beautifully but is now using a fair bit of oil, about half a litre a month. I have had it regularly serviced but my garage cannot identify a leak but they are not Audi specialists.

Might be worth speaking to Audi independent specialists around Oxfordshire to get different prices. 

Welcome Martin and thanks for joining. 
Engine reconditioning is now a thing of the past, and without a doubt, an Audi dealer wouldn’t undertake that, even if you pay them thousands of £. Fitting a new engine (if available -in caps) perhaps, but that would seriously damage your wallet.

Some engine reconditioners remain, but their trade would generally come from the classic car enthusiasts, or possibly extreme tuning. In effect, I think you can realistically forget the idea. 
Your oil usage equates to approx. one 5 litre container of oil a year - < £50, even for good stuff. 
The only caveat would be if it is seriously affecting emissions. 
Regards,

Gareth. 

Thanks Chaps, any informed intel is useful