Running get_iplayer with no options, I get programs listed like this:

  b05zh5dp: 349 Clangers-The Lost Notes§

(I recall setting the separator to § back when I had my wits about me)

Is there any other information that I can get about this program? I've seen samples that contain the Channel, so presumably there are other fields available to display.

I can probably manage by myself once I know what fields are (still) available. I'd been using <categories> until recently...

If you run --info on a programme you will see more, but that extra data can't be used to help in searches.

Look at the first line of your TV cache file ($HOME/.get_iplayer/tv.cache or %USERPROFILE%\.get_iplayer\tv.cache on Windows).  It shows the fields available for search results (used with --listformat).  Aside from the ones you already use, <channel> is probably the only useful one to add.  For full information on a programme, do as tvfan instructed.

BTW, there is no need for a separator.  Only one programme per line is listed in search results.

I looked at my tv.cache and found that it contained ...|categories|...

If I run the command:
get_iplayer --pid=b05zh5dp --info
... then I see:
categories: Children's,Entertainment & Comedy,Animation

So then I run the command:
get_iplayer --refresh --listformat="<pid>: <name>-<episode>§<categories>" > tv.txt
... and tv.txt contains the line:
b05zh5dp: Clangers-The Lost Notes§<categories>

What am I doing wrong to get "<categories>" where previously I would have got "Children's,Entertainment & Comedy,Animation" ?

As tvfan said, information available with --info is not available for searches.  And as I said, <channel> is probably the only useful additional field to add to --listformat.  As for why you see no categories in search results, read the latest release notes.

Thanks for all the help understanding this. I find the categories more useful than the channels as I prefer factual programs no matter what channel they are on. I'm using a program of my own to create a PVR-like experience, so I'll investigate using --info against all the PIDs, one at a time, to build an index that *does* contain categories.