Thanks for all your help on this one. We're winning slowly having
followed various ideas from several individuals.

I've managed to get sound out of the system using OSS.
I also needed to adjust the sound card settings in the BIOS as they had
been set to non-standard values. As the box came from eBay, I have no
idea of its history and should probably have checked this before. :-/

As I say, I have got the OSS test sound to play, but when I try to use
mpg123 I get an awful howl and then the system locks up.

Tom