I went looking for this in the supermarket (Sainsburys) this morning and couldn't find any.
What shelf is it likely to be on - I looked mainly in the baking ingredients aisle, next to the candied peel and cherries. They did have candied ginger but no crystalised ginger.
I have got some stem ginger in a sugar syrup though which needs using up. Do you think that will work in the ginger biscuits.