Have you read the many "fixed versus variable" threads that already exist? If you fix for 10 years and find that you want to clear/reduce the mortgage early or move house/mortgage provider then you will be hit with huge fixed rate breakage penalties. Only fix if you really need to - i.e. if you are under cashflow pressure to meet the existing variable repayments or would be if rates increased by a few percent. Otherwise stick with a competitive tracker rate.