The interest that you pay on a business loan will normally be considered a business expense, which will reduce your net profit and hence any corporation tax liability. The capital repayments are a cash flow item and not deductible as an expense.
If tax efficiency is important to you, you may want to consider leasing or contract hire. With these products you pay a monthly rental to use the asset and this rental is normally fully deductible as a business expense.
You should talk to your accountant for advice on your individual circumstances.