Thanks for all of the replies. The routing for the trip is:

ICN-NRT (JL C class)
NRT-LHR (BA F)-VIE (BA C)
FCO-LHR (BA C)-NRT (JL F)
NRT-ICN (JL C)

This is an AA 140K First class award ticket. When I last checked, the LHR-NRT route, which we am currently booked on with JL also had 2 BA first class seats. This was the flight I was wondering about changing. From the different comments, perhaps I should try and get JL from NRT-LHR in F instead of BA!

On the BA flight we currently have 4EF booked, and on the JL flight- a 777 with 9 solo seats, we have 2 C and D.

I suppose we were lucky to get First class seats into Europe for Christmas! BTW, and thoughts on the best way to get from Vienna to Rome? I was thinking the train might be good. Oneworld carriers seem a little out of the way (via LHRor HEL) or expensive (via BUD)