Hi Kevin,
Thanks for your reply - I am not at the office at the moment but will look at getting this when I can.
I did not think that changing the value in a 'where' clause would affect the execution plan but clearly it does. Is there anyway to force the view to be treated as a table, as in
Select * from vwSalesResults into #temp
Select * from #temp where HeadOfficeCode = 'BBB'
Andy