The execution plans are about the same. It's on the IO stats that throw up the difference with all those reads to Worktable in tempdb. Something is obviously triggering that but have no idea how to find out what.

I cut out a part of the sproc which I identified in Profilier as the statment that was causing most of the duration. So, the io stats are from a query in SSMS, no parameters or whatever.

Clive