I wasn’t familiar with the Jeffries but i used the following for my reference :
https://www.concertina.info/tina.faq/images/finger2.htm
Comparing it with the Hayden it does seem a bit more complicated because of how the notes are placed on the buttons. But i guess once you start playing something new,it takes a while before you get the hang of it.
I was concerned about being able to play accompaniment. Thank you for pointing out that it has a a lot of flexibility in that area.