What if the lender's forecasted interest is greater than what I actually borrow?

You should only pay for the interest that you use. Most lenders charge daily interest. Some lenders still charge monthly interest (although it’s much less common then it used to be), which means you may pay a full month's interest if you redeem partway through the month. The lender will confirm the interest in a redemption statement at the end of the loan. For development and refurbishment loans, lenders tend to want to hold more interest than they think will be needed, so that they don’t have to ask borrowers to pay interest partway through the project.