I can think of no reason that would preclude English concertina, in the right hands, from playing Irish music but perhaps it's a bit like the old piano accordion vs melodeon/anglo for English dance music. Dancers seem to like the lift inherent on a push-pull instrument. It's very easy to play the English conc/piano accordion in a less than rhythmic style whilst the push-pulls almost impose a rhythmic style (of course this can be c*cked up too if you try really, really hard).

Fliss, I wouldn't dream of picking you up on spelling etc - you're quite right, it is rude. So I won't. (notice apostrophe in "won't" same as in "don't" - I'm joking honestly)