I suggest that you have clear grounds for rejecting the vehicle as unfit for purpose and getting your money back, plus www.honestjohn.co.uk/faq/consumer-rights/

It is a know manufacturing fault which, frankly, it is appalling Audi are not covering as a goodwill gesture. The TPI are Technical Service Bulletins or whatever Audi choose to call them.

That's by the by - I can't see you getting a full refund as you've done 6000 miles so clearly had use of the car. Refund wise it will be the price of the car less depreciation, wear and tear and the mileage.

If you can get the £1000 I'd be tempted to shop around and see what the job can be done for. Avoid Audi main dealers - maybe try a specialist. If you can get it done for £1500 I'd be tempted to stump up the £500 and just put it down to experience.

I have built and rebuilt several engines for the road and track over the years, always from salvaged engines. I have yet to find one where a simple re-ring would have worked successfully when the engine was worn. The top of the cylinder usually suffers from wear on the thrust side of the bore and in this area a new ring would never seal, the original would undoubably have sealed better. Because of this a rebore is required which obviously requires new oversized pistons. Since I have always done the disassembly/assembly myself the only costs have been the rebore and honing but good quality parts are not cheap.

Many manufacturers provide service/exchange short engines for these eventualities at a cost far lower than a garage rebuild. Several years ago I was rebuilding a Zetec 2 litre for the track, needed new pistons/rebore and while it was in bits it was sensible to replace the bearings and all the seals/gaskets. The cost of parts and machining was over £600 plus my time. Instead I simply gave our local Ford dealer the old short engine and £400 for a brand new (not reconditioned) replacement (with a garantee).