The zoom drivers will not work on a UK supramax - it's a conexant chip (rockwell) not lucent as you said - the only 2 drivers i have got to work with my modem were the s3 ones (work fine) and some generic conexant ones that i downloaded (they lit the modem - but couldn't dial out)
if you can't get the s3 drivers to work one suggestion would be to clear out all the reminents of failed installs and try again. You don't need to re-install w2k to do this - just delete the relevant .inf files from the w2k inf folder - usually oemx.inf and try reinstalling again. I can mail you the Conexant generic driver - it didn't work for me - but might for you - just let me know.