Nat, I'm quite surprised at your experience. For when only a teenager, I used to go to Boots a lot, asking for various chemicals that I had read about in chemistry books - mostly to make fireworks! I often requested (and got!) sulphur, saltpetre and embalming fluid (to use as a film emulsion hardener) over the counter no problem or questions asked.
Like you, in my later years, I did a lot of wine making but by then citric acid, along with a lot of other things, were boxed or jarred up and were for sale, quite openly, on the shelves. I must say that I've never heard of the connection between CA and drug users before though.
Terry S