OldTurkey
Happy new year and thanks for your reply.
I had found the first site when I first tried to solve this problem. The author indicates that his solution didn't work permanently (only for "several weeks"). This is why I was trying to find a way to do the hardware mod of hacking out the temperature sensor - a method which seems to be universally successful when applied to 15" and 17" models. Despite all that - and I'm really no whizz with the Terminal - there's really nothing to lose so I may give it a go anyway.
The second link gives me a 404 error.
If your mission digs anything further up, I'd be very grateful to hear it.