Try the music room (www.the-music-room.com)
They sell the Handbook for English Concertina, in their catalogue it says "A clearly written method for learning the English Concertina, with the aid of diagrams and an easy to follow text.Fingering charts and photographs throughout.Contains a section of tunes with fingering for each note.Concertina care and maintenance is alsi covered.Exellent Value" the book is 4.95 English pounds.