[20 Key Concertina]

While looking for a new concertina I've come across a bunch of nice 20 key Anglos at a cheap price compared to 30 key instruments, I was wondering how restricted I would be in terms of what I could play if I went with a 20 key instrument. Also I have seen some 26 key models, do these offer significantly more variation over a standard 20 key or just a little bit? 

[Wheatstone May Fair Anglo Concertina]

Thanks for the suggestion, I'll check it out!

[Wheatstone May Fair Anglo Concertina]

I'm a beginner player who is looking to upgrade from an old East German Anglo, I found a Wheatstone May Fair Anglo selling for about $1100 and I was wondering if this concertina was any good and if it was a fair price for it. Or if anyone has some recommendation for other 30 key Anglos, preferably a little cheaper.