I also have the same programme as a different file:
Caroline-19891230-DaveFisher-30min.mp3
Dave Fisher was indeed hosting for both occasions (morning of 29th and 30th) according to CM Bulletin. This also seems to be just the first 30 minutes of the programme. There don't seem to be any edits and Dave reads a weather report near the end:
Cold, fog, min 0 degrees C, winds E light, sea slight, vis. mod.
However the correct time and date is most likely 0000 - 0031 hours on Saturday 30th December 1989 (that is midnight of the evening of Friday 29th).
I think it's just the fact that the programme is at midnight which caused the confusion with the file names.
If you listen to the file "Caroline-19891229-2215-2300-ChrisCooper.mp3" (which is a studio recording; very unusual), Chris Cooper gives exactly the same weather report at 17m40s (so, 2 hours earlier than Dave Fisher's re-reading of it).
EDIT: By the way, I checked the Janfrevos site first... the same programme is listed twice!