Result - it worked, no drivers needed, no hassle whatever. And since bluetooth isn't especially fast there won't be a problem with the computer having USB 1.1 ports.
Don't actually NEED Bluetooth for anything on this computer, but it's good to have the capability if needed.
I should add that I haven't tested bluetooth communications yet, since I don't currently have any compatible devices, but it's certainly being recognised by the computer.
later - and to add to the cheap bastard theme, I just picked up a mouse, keyboard, and speakers on ebay for 99p plus postage! REALLY good news, because my current keyboard turns out to have a small flaw - the main "Enter" key doesn't work! Fortunately the other Enter key does, so I can use it after a fashion, and if it dies more before the "new" one arrives I have another USB keyboard somewhere - it's windows, not Mac, but should still work.