They don't have any ID3 tags at the moment.
It's apparently possible to store ID3v2 tags in .flac files -- the reference decoder will skip them.
(Hmmm, wanders off to a shell prompt)
OK, this seems to work:
$ id3tag -2 -a "J.K. Rowling, read by Stephen Fry" \
-s "The boy who lived" -A "Harry Potter and the Philosopher's Stone" \
-t 01 -T 07 "01 - Chapter 1- The boy who lived.flac"
$ grep `flac -c -d "01 - Chapter 1- The boy who lived.flac" | md5sum` MD5SUMS
Shows that playback is unaffected.
$ for i in *.flac ; do \
flac -c -d $i | lame -v ${i%.flac}.mp3 ; done
Gets you the MP3 file.
$ for i in *.flac ; do \
id3cp $i ${i%.flac}.mp3 ; done
Copies the tags across -- except that there's a bug in the 3.7 version of ID3lib that makes this not work properly. It works OK with (what I think is) the 3.8.0-pre1 version.