CS were your snowdrops the 'standard' Galanthus nivalis type or some other species? There are several different species and some may even be autumn flowering.

Actually, I went looking for wild snowdrops (G. nivalis) earlier this year and, if anything, here in South Manchester, I thought that they were a bit late. I did actually find one of the other species (not an autumn flowering one) but by the time I found it (in March) I was too late and it had finished flowering (I knew that it was a different species because it had broader, pleated leaves).