Hi Orma and welcome to this very helpful and friendly Forum.
CBA tutor books are not exactly thick on the ground but one I can definitely recommend is the French one by Florence Glorion. It costs 58 Euros which at first sight seems expensive but includes a web site password where you can download a really excellent English translation plus sound tracks of the tunes in the book along with masses of other generally interesting things and information. Her colleague, another Florence, teaches Diatonic (Melodeon) Here is a link.
http://diouflo.com/english/shop.html#recueils_chrom
My partner Marjorie is using this book having recently started on CBA - C system (Weltmeister Romance 602), and I liked many of the tunes so much myself that I have been trying them on my PA !! Some are traditional and some have been written by Flo though all are very French as you might expect (and none the worse for that I would add). The book pushes along fairly rapidly, each turn of a page leading to some new technique using comprehensive CBA tablatures (including nominated chords and no bass clef - hooray). The two Flos run courses in Brittany which we would just love to attend. Flo is very friendly with email too.
Brace yourself ….. and happy squeezing ! Marj says to tell you not to despair at first, it really does get easier eventually !!