I'm the journalist who was looking for interview subjects last month. The article has, at long last, been published.
Among other details, my article features a history of HPPD that stretches back to the 19th-century; several real-life case studies; discussions of HPPD's link to psychosis, alcohol abuse and suicide; and what the condition may mean for the promise of future psychedelic research.
You can read it on The Independent here: https://www.independent.co.uk/independentpremium/long-reads/netflix-good-bad-trip-lsd-psychedelics-never-wears-off-a9533136.html
It's behind a paywall, but you can create a temporary account through Google or Facebook pretty quickly. If you'd rather skip that, you can read a less fancy-looking version here on Pastebin: https://pastebin.com/R9jy1NWV
Thanks - enjoy. Let me know what you think.