"But maybe owlgal is thinking of a sort of combination, such as a weekend (or week, or series of evenings, or...) where several individuals each build their own instruments from supplied parts/kits under the watchful eye and direction of an "instructor"? I believe there's an annual event in England for doing just that with melodeons, but I haven't yet heard of one for concertinas."
That's exactly what I mean :-) I also just received the repair manual book which will be interesting reading.