Hi. Anglo key availability dependes on where you look.

Most of the old concertinas were C/G since this is a good configuration for singing to. Songs in C are common. Tunes in G are possible and both Bb and C# are on the third row of a 30-button instrument, so D and F, popular song and tune keys, are also possible.

A G/D Anglo can manage F, but you require two notes from the accidentals, one of which is the fundamental (F natural). No chords easily available as a result.

Most new concertinas are G/D and a lot of the players can also play melodeon.

I got as far as trying the Anglo for a while, and just about getting my head round the usual chords and runs on a C/G in G and D, but I'm left handed, which presents no problem with my English but screwed my brain on an Anglo.