My understanding is that QR won't bargain the Avios amount. You could consider small claims court. The DOH-NBO is only a portion of your ticket (which you can probably approximate), and part of that is the comfort that the seat provides. Given that the difference between Y and J is usually <X> (best if you can express X as a percentage), then you are owed some of that difference. Note that you did get the better food in J + other benefits, so the difference in the seat alone is only part of it, tho arguably even a Y seat reclines a little.

Chances are QR won't show up and you win by default, but you might have a case nonetheless.

Disclaimer: I have NO legal qualifications and this is not legal advice.