Should I fix my interest rate? What are the ramifications?

Fixed interest rates can allow better forward planning as you know what your repayments are going to be over the period. People fix rates when they believe interest rates are rising and want to keep the low repayments.

On the downside, if the interest rate falls, you still have to pay the fixed rate agreed upon. There are also break costs if you pay off the loan within the fixed rate period. There is a certain amount you can pay off without being penalised, but that depends on the lender.