OK ... so I solved my own problem in the end ... not to my satisfaction and no thanks to FS tech supp or warranty department who passed me from pillar to post an would take no responsibility for the problem! Rant over!
You have to attach an external USB DVD drive to your PC ... press F12 at boot up to select the boot device ... select the USB DVD drive having already inserted the XP Twinload DVD ... Agree to downgrade and off it goes ... when it asks to reboot unplug the USB DVD and then reboot ... XP starts up just fine
... The DVD drive works perfectly under XP from then on.
This does not address the issue of Vista Business not being able to read or access the DVD drive in its pre installed state ... I've tried changing the DVD drive, the HDD and upgraded the BIOS ... nothing works ... I've had 3 of these machines so far from eBuyer ... all the same (no blame on eBuyer!).
As with most things in life "Vista" is a pretty view, not an operating system
Cross posted to other threads with similar issues! ... FS will probably moderate as I've been critical.