Hello - it's not Thornes. They have been at 3 High Street since at least the 30s and that building has a very different style of brickwork around the upper windows. It's also on the flat, whereas this building is clearly on a slope. It looks to me more like the buildings on the north side of Station Road going up the hill - there are a few of buildings of this sort of style roughly opposite the post office - I know they used to be (ten to twenty years ago) Classical Rock, the Harpenden Building Society, Simmonds, a photo place I forget the name of and a couple of others. I haven't been back for some time though, so I don't know what they are now.
I've also had a quick look at the Hertfordshire Kellys Directories in my local library, but there's no Rymells listed for 1906, 1929, 1933 or 1937. They didn't have any more recent directories to check, so if this is Harpenden it'll be post-war.
Good luck
Richard.
