Thanks for the information Bill!
As for what I plan on playing...I am not entirely sure. I have in my mind that I'd lile to try sea shanties and irish.......jigs..reels...hornpipes, etc.... but that may change. I am not sure if this broad interest lends any clarity to my anglo vs english choice or not...but if it does...please let me know.
I currently play 2 other instruments: old-time frailing banjo, and crossharp harmonica. I have a secondary interest in trying some sort of duet with myself via multitrack recording. The banjo plays in key of G, A, C, and D. And I have harmonicas in several keys. So a song such as Fisher's Hornpipe, which I know on banjo, might be fun to learn on concertina as well.
I've been doing a little more reading....perhaps you can clarify. A 20 button D40 Hohner anglo would allow me to play a particular song in a particular key. And a 30 key anglo would allow me greater ornamentation and flexibility on this same song...as well as play songs in other keys?
Many thanks for the info...I really appreciate it.