I have sort of found a solution to the above, however it is not a very good solution - So does this mean Excel 2003 is not certified for use in Windows 7 ?
If you go to
Control Panel > All Control Panel > User Accounts
then click on "Change User Account Control settings"
then drag the arrow down to "Never Notify"
Re Start your computer - then Application.SendKeys starts to work.
Hmmm not a very good solution, any better way of achieving this ?