Thanks for all comments. Downloading the XFree86 4.2 from the Net is not feasible for me, as I have only a 56k modem. I had a go building the source code (which I have from a magazine coverCD): this went well until I tried 'startx' and was told, "/usr/X11/startx: no such file or directory". Interestingly it didn't say 'no such command.
I finally got X 4.1 working by ticking the VESA option on the video chip dialog, and making sure the default horizontal and vertical sync rates were below 60Hz. VESA (Video Something Standard Architecture) was an option my old SuSE distro had for if it couldn't recognise video chips. It seems to work: there's an odd flicker for a very brief moment before twm comes up (Yep, twm on a Thinkpad A31p), but then everything works fine. Big question : Is it safe, or am I potentially damaging my hardware? Best Ivan