Okay to re-visit my original premise that I had a problem I ran my test with XP again today to find that it was reporting the same speed as Vista! Previously I was getting 28K+ down and 750+ up on a ADSL2+ bigpond connection.
I talked to a friend of a friend and was told Telstra are doing work on the Brisbane hub that 'might' cause speed issues.
As both systems are now reporting the same speed 9k+ down and 750+ up I really can't blame the OS but certainly can blame Telstra for a crappy service!
So this might be a case of crying wolf!