Oil Consumption worsening

Hi All,

I'd previously had a thread on here explaining my car's issues but the situation has worsened so I thought it might be an idea to start a fresh thread and seek your collective advise.

I bought my car privately. It's was at the time a used (full s/h) A5 2013 FL 1.8 TFSI with 64k on the clock. I've had it almost 18 months and put about 18k miles on it since.

Upon initial purchase, immediately, the oil light came on and would require a litre of oil every 550 miles (occasionally this number would rise to as high as 700 miles depending on driving conditions but 90% of the time it was always 550 miles).
I took it to Audi, who confirmed it was consuming oil however they couldn't help as my car already had the updated piston rings etc. So, since then....and some 15k miles later I've just been topping her up with oil and life's been fine.

This last month or two the oil light has been coming on at just 250/300 miles. I swear I can see more exhaust fumes... though tbh...this might be paranoia as I've always 'seen them' ever since the first oil warning light.

Clearly the situation has gotten worse and I'm at a cross roads. I wouldn't sell the car privately as I've too much of a conscience to do that. I don't really have the money to P/X it against anything I truly want (I also love the car and seemingly everything else is fine) so I'm wondering whether to explore a repair?

If so, shall I just keep driving it until it finally gives up the ghost and then fix engine then?...or by waiting could I somehow make other situations worse? If I seek to repair it should I rebuild or just swap the engine out?...and given it's not the piston rings what would the problem be likely to be? (I'm assuming its not the pistons rings etc)
Lastly, 'if' I had to swap out the engine, I'd feel happier if I upgraded (it would feel like less of a waste of money etc) so is sticking a bigger engine in a possibility....or am I looking at more potential problems?

Any advise gratefully received!

Thanks,
Greg