For a site with an extensive collection of Excel files for both GCSE and A level – see Mike Hadden’s MathsFiles site.
There are other resources also, including some for Autograph.
A useful feature to help explore the Excel files is the option to see a screenshot.
These spreadsheets could be usefully used for demonstrations in the classroom and students could then study the examples further themselves.
The A Level files (scroll down the page) include resources for Statistics and Mechanics as well as Pure Mathematics. Files include some for Further Mathematics, for example Matrices.
The Statistics resources include a Normal trainer with the option to study ‘backwards’ problems and a very clear contingency table calculator.