In the face of such comprehensive and conclusive evidence I shall forthwith place an order. Supply in France is not quite so easy and as I've spent some time searching it all out I'll share the results for the benefit of other french researchers ( ??! ).

These three all do scies japonaises:

http://www.ftfi.fr/
http://www.hmdiffusion.com/
http://www.bordet.fr/pages/

The latter offer them in longer lengths (to 300mm) and also supply some Silky saws. These latter are also available from elagage (tree-surgery) suppliers:

http://www.elagage-hevea.com/
http://www.arbres-online.com/

Silky saws are either curved or straight. Certain of the models which Tom reccomends are not offered here, but the Gomtaro is straight and available from the last named supplier.

Again, thankyou all for all info.