Dan Shotton was a student at the College of Art and Design in Bristol, and learned his frame building skills working for Argos frame builders . I knew him as a fellow member of Bristol Road Club in the early 80s. He made only a small number of frames, all high quality, and so far as I know, all with "DS" at the top of the stays and with "Dan ..." frame numbers. I have a 1982 DS frame which looks as if it might be identical to yours, recently resprayed by Argos, who did a fabulous job, including re-creating the intertwined "DS" head transfer. Your frame sounds very much like one of his.
I recall he was keen on cantilever brakes.
I had thought Argos didn't apply their own transfers to other makers' frames, but recently saw what looked like a fairly basic mass-produced 1980s frame with an Argos respray - certainly not the sort of frame Argos makes. I would guess yours is a Dan Shotton frame with an Argos paint job.