OK.

In the 'Profile' section of 'User Properties' in 'User Administrator' on the PDC (we have only one PDC) I have entered:
'Script1.bat' (the .bat file with the KiXtart lines in it)

The KiXtart files are all placed in the netlogon share of the PDC.

Interestingly from the command line on the W98 box I can type:
//eugene/netlogon/Script1.bat
and it executes the KiXtart script OK.