Tsql timing out on deployed server

I have some TSQL which is fairly complex it is a series of unions collecting data over 6 years (about 25,000 rows) it splits the data into years presenting each year as a column (not a pivot)
it is called from an aspx page using c#
My Problem is The TSQL runs Ok in a few seconds on the development machine which also has local data. It times out on the live VPS server both when I run the aspx page and when I run from within SQLSxpress management studio
I suspect it will be something to do with the enviroment but I have no idea where to look, perhaps someone out there has solved a similar problem????
jnc
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