>Hare motif...French and Moravian
Duck motif...Polish
Fish/angler/net motif...French, Moravian, Polish, Serb and German.

Aren't these almost invariably in the English versions as well? "Rushes a-growing" appear less often, but then there are so few texts that it may well mean nothing.

Do we know that the continental versions antedate the English, including Lover's?

I would expect not - which leaves us nowhere in terms of the direction of influence.

The wide distribution of the European cognates, however, does suggest a very old oral tradition.