No, I thought of the "timestamp" thing myself, but unfortunately, it's still too ambiguous. In most cases, I don't know exactly when they were created, or a lot were created or accessed about the same time, so it doesn't narrow it down far enough.
If I pick the one I think it probably is, there's still a good chance I'll get it wrong, and delete one that was OK. I suppose I could go through the tedium of renaming them one at a time, see which programme disappears (if any), then restoring the name. But it doesn't seem worth the time and effort.
Seriously tempted to just dump all the downloads, and give up on iPlayer altogether. You reach the point that if there are too many obstacles, you stop wanting to watch the programme any more.
I have had problems previously with Adobe Air. It wanted to reinstall it every download, even though it was already installed. If I refused, it wouldn't proceed with the download. If I said yes, the install would fail anyway... Catch-22.
This is what I meant about never got it working right.
But I thought things had finally settled down with more recent versions - it's no longer repeatedly asking for installations of things it's already got. Just doesn't work anyway - or at least, can't record a whole series, without screwing up at least a couple of episodes.