Hi, Paul,
Unless there is some supporting evidence for this to be Convallaria majalis var. montana, I'd suggest it's the usual and very common European Convallaria majalis instead.
The most noticeable feature that distinguishes Convallaria majalis var. montana from the very commonly-grown Convallaria majalis is that the midribs on the flower tepals are green, unlike on Convallaria majalis - your plant doesn't appear to show the characteristic green-striped flowers.
If you take a look at the comment posted for this entry, you'll see what makes Convallaria majalis var. montana different from the Convallaria majalis that we all grow. (And I'm not meaning to single out your photo particularly - the majority of the other photos posted under Convallaria majalis var. montana are probably actually just Convallaria majalis also.) Please let me know if you disagree.
Thanks,
Lori
