I have been working with the Excel template from microsoft that
calculates my loan repayments. This has been OK if the loan is paid
out in full by the end of the contract.

I need a template that has a balance owing (residual or balloon),
even better, one that I can enter the % residual and compare loans if
need be.

This is needed for two reasons.
1. to work out exactly what my principal and interest is each month
2. to compare different residual options for loans