if you have been playing guitar and understand about chords,Iwould recommend the English.Everything Alan and chris say,I can confirm I have been playing thirty years, with no tennis elbow problems,I rest the concertina on my left knee,and have my thumb straps very loose,so ican move my thumb with the rest of my fingers.
I,ve two tutors,http;//www.dickmiles.com
one which deals specifically with song accompaniments.