Syringa is a Genus. All lilacs are within that Genus. Yeah I was reluctant to say Lilac because of the leaves.
Thanks saltcedar, that does look close. I had no idea lilac leaves could look like that... That does seem to be the correct species. I can't find any info on a similar cultivar: the leaves of this one get white highlights when exposed to sun, and are larger than the specific descriptions I've found for S. villosa, by memory they are about 10cm wide. It's really quite striking.