Quick Update - Thank you for the proposed destinations, i called again hoping i would get a different answer. I tried every UK destination that Qatar flies to (did some research on their website beforehand to no avail). There was no availability whatsoever. Might there be a max capacity between the Japan and UK market in place? Regardless, i settled for CDG and it has been confirmed. I booked a flight from CDG to LHR with BA using avios which will now be on a different ticket, i am hoping 3 hours will suffice.

This brings me to another question, will QR be able to check my bag all the way through to LHR as BA is a oneworld partner and the transit is way above the minimum transit connection time? They are two different tickets, my BA flight from CDG-LHR is in Business Class as well so baggage restrictions should not be an issue. Iv had this experience previously, its a hit and miss, but having them check it all the way through from NRT-DOH-CDG-LHR would really save me a lot of hassle at CDG and i could transit airside.