Well I got there in the end...
I think the first possible cause of the previous problem was I was pointing to a file location for the drivers, which had several inf files therein. This time I pointed to the actual P2k file.
However using the one in the link message saw me have a device not found error (this was dated 11-6-2003) for the motorola usb modem. Somehow I found myself at a directory offering me another example of this file (dated 8-25-2003) I selected this and things were starting to improve.
Next however I had the missing file error again - this time though it was named as usbserv.sys. A quick search showed this in several directories on my system, so I pointed the software at one of them directly and it solved that problem.
So its now interfacing, the on screen picture is marginally different but it works.