Well Sian, I do know a flute player/ singer from Anglesey named Jeff (or Geoff) who has been a regular on the Friday night sessions for a long while but I'm not sure he's the same person and I don't know the band.
It is possible of course that the Nelson do have another night or that the session on the Friday has shifted in direction. I've been out of North Wales for over a year now and wasn't a regular for at least the last two years of my living there (I loved the session though, it always was my favourite in my area).
Total thread drift but the session I used to go to started in a pub called the Ship Launch at some point in the 1960s - well before my time and seems to have the version of Napoleon Bontparte in the dt credited to Tommy Flynn the landlord there... On the Sunday at the end of the Bangor weekend, we sang the song and someone asked if any of us remembered Tommy Flynn and there was not one of us present at the time who had ever met him.
By the strangest of co-incidences, when I went to the Norwich session the following Tuesday, I mentioned the trip to Bangor and one of the regulars took an interest. It turned out he was a student there at the time and had a lot of memories of the early days. I think I learned more about the Bangor session that night than I did when I lived near by.