Sarracenia purpurea has two subspecies, S. purpurea subsp. purpurea, and S.purpurea subsp. venosa. The latter is the more southern form of the species. It can be distinguished from subsp. purpurea by the following traits: Outer surface of pitchers is pubescent. Pitchers are shorter in length than those in the northern race.
As for carnivorous plants to try in Scotland, I would think several of the southern trumpet pitcher plants would thrive. I grew them outdoors in pots when I lived in Vancouver BC. Sarracenia flava, and Sarracenia leucophylla both make a real statement in the garden. I didn't venture as far as to try the Cape Sundew (Drosera capensis) outside year round , but there are reports of it surviving year round in coastal southern British Columbia.
