The two titles were previously only available by ordering The Derek Smith Omnibus. As of today, each will be available separately, albeit without the Bob Adey introduction and the background material (just the texts, ma’am, just the texts) , which makes them much more affordable.
Model for Murder will not be made available separately. The lead character is Sexton Blake and, although I sneaked it in at the back of DSO, I’m rather more sanguine about offering a much easier target for copyright infringement. I did try to discover who does own the copyright, but that’s a mystery in itself.