andy-hughes - I would totally, totally disagree.
'Hurt' by Johnny Cash is, to me, an emotionally devastating song. 'Hurt' by Nine Inch Nails I couldn't care less about, when I first heard it and even after the Cash version turned me on to the song - it means nothing to me. The emotional impact and the meaning, as you put it, is totally different.
In fact, Cash didn't even think much of the song before he got involved but loved it once it was recorded, and Trent Reznor has since happily gone on record to say the song is now essentially Johnny Cash's.
Context and delivery is everything with words you know! To say the meaning of a song is unchanging and immutable is ridiculous. And to say that the BBC AND each member the assembled talent were unaware of any possible negative connotations in singing 'Perfect Day' is doubly ridiculous!! Why was it OK then? Because the meaning of the song was changed and made into something different by the way in which it was used.