Ok I worked it out for myself. Just to let anyone know.... the XP 64 driver DOES work on Vista 64 in my experience, just as others have reported. Heres how it went for me.
I installed the XP 64 driver with the correct settings on setup, (service = pppoe and the vpi-vci = 0.38 for uk ) Then I carry on and let it install the drivers as usual.
Windows does not find the driver (wich is the same as in 32vista) so I go to control panel, and then device manager, and find the speedtouch330 lised under "others" (until its installed). I right clicked on it and clicked on update driver.
The green lights apeared on my modem.
The setup program then carries on to TRY to find my modem ( even though the green lights are on and the drivers are clearly installed ), but the program fails to find to it, so I quit.
Then I ran speedtouch 330 driver for vista 32 bit, It doesnt bother installing the drivers as it already finds them, and then it carries on SUCCESFULLY to the second half of the install ( that the other setup program failed to do ) where it makes a connection and allows you to enter you ussername password.
and Bingo, I was connected. This was just my experience, there maybe easyier ways of doing this, but thats how i did it, hope it helps someone.