Here’s an update.
Following up on a post in the Cover Versions thread, I happened across this site:
(I’ve set this up to go straight to the sessions listing.)
This is the most comprehensive Peel session listing I have found. What it doesn’t do is link you directly to an online recording of a session (indeed, there may be no such recording available); but what it does do is allow you to see who recorded sessions, and when they recorded them.
From that point onwards, happy googling.
j