What software to use for budgets - manufacturer with 750 nominal codes?

My scenario is this:
£20m Manufacturing company
Accounts on Sage MMS
8 Production departments

Production overheads are absorbed in to WIP at annual rates.
750 nominal codes.

The budgeting model I have inherited runs to 30 Excel sheets, 60 000 calculations.

You change one number, the whole thing recalculates.

We go through a few budget iterations, and then someone wants a comparison with an earlier version.

This is a nightmare.

What software is there out there to manage budget creation?

We are looking for budgets broken down in to months.
Tom Cadogan