Simon,
Thanks for the top tips. You are right enough that it should have had ribbons or marks where the ribbons were, but totally absent.
Unhelpfully, the Service Number appears in the London Gazette online as a Lt commissioned in the RAMC in 1943: P.B. Wooley. I would not have thought that officers' S/N were re-used. I received the 1950 edition of the Army List from my library, but no G.S.Atkins (or Atkinson) present, and no listings by S/N. I will try to order a 1953+ copy.
There are old holes of collar badges however. 25mm apart, side to side. I thought that the Cameronians did not adapt collars until the Brigade system robbed them of their cap badge. Either way, the common collar badge was the mullet and bugle horn, I believe the lugs were up-down.
I found an interesting photo online. The jacket, dated 1937, is similar (but not Highland cut skirt) and the collar badges are bugle horns that may fit the pattern of holes. It is described as a Scottish Rifles (Cameronians) tunic, so I wonder given that the 2nd Bn (merged late 40s) always titled itself the 2nd Scottish Rifles, that this may belong to a Scottish Rifles-affiliated Cameronian TA battalion. The plot thickens, the link is here and the photo below: