I'm back. And the package I was worrying about had arrived, containing this:
The 1984 Allison & Busby edition of Richard Stark's Slayground. It has a 2cm tear to the front of the jacket and the spine's a bit faded, but considering what I paid for it (not very much) I can't complain. And it's arrived, which is the main thing. (Of course, there's still the other outstanding package... but that's a worry for another day.)
Slayground is the fourteenth Parker novel, but curiously it appears to be the first one A&B published, before Point Blank even. No idea why that's the case. Perhaps the rights weren't immediately available on the earlier ones... Or maybe they figured they'd start with a really good Parker (Slayground is supposed to be one of the best in the series). We may never know.