It's hard to be sure from the distance in the photo, but I'd hazard an educated guess at Buxus microphyllus - dwarf Box in other words. Doesn't flower, but will eventually create a low, mini hedge. Flowering options which keep their leaves in winter and remain fairly neat, but will remain much lower than the Buxus in the picture, hmm, well, Campanula portenschlagiana (used to be Campanula muralis, still sold as that sometimes), or Helianthemum, which does prefer sun and will need cutting back after flowering to stop it sprawling too much. Otherwise, Hebe youngii. If you want a low hedge effect without flowering, then Euonymus microphyllus comes in two variegated options.

I'd go for buxus too or there is the small euyonoumous that is tough as nails and very hardy.

Thanks so much, both. :) How tall does Euonymus microphyllus become? Some sites say 20cms, others say 1m (!).

At maturity, it'll be a metre, but its quite slow growing and responds well to clipping or pruning.

Thank you! :)

Or you might consider Ilex crenata - looks just like box but no danger of the disease that's killing a lot of box now.