OP, Glad you got a satisfactory outcome! As you said it’s always best to do your own research and phone up.
I had a J HND-LHR avios is booking cancelled last year and was automatically rebooked in Y on JL via Paris. I searched availability and phoned up clear that I wanted to be rebooked on Finnair. Had to stand my ground as they tried to argue I’d accepted the flight change but eventually all got sorted. The Finnair seat was great as well.


Hope you have a good Flight!