This morning I was beginning to wonder what I'd been smoking ...
Last week I definitely took 2 copies of each make of my old media in to work, and all 4 items both erased and burned on the 52327S there, without a hitch. Today I figured I should re-run the test, and got repeated failures on the two Philips CD-RWs! (But the one Lead Data I took in was fine).
I still find it puzzling but in the circumstances I don't think it's worth imposing on work to try my drive there; instead I should accept rdgrimes' advice that the media are not good, and replace them with better stuff. Something I was reluctant to do, as when I bought them the Philips were said to be the best (and cost accordingly), and although they're old, they've not been re-written that many times. At least media aren't that expensive any more, and I'll be able to burn faster, too.
I want to thank (not a strong enough word, really) all you guys for your help and advice. This is a great forum, without a doubt.