dkid

You could go onto any lenders SVR and benefit from cheaper repayments until it looks like base rates will rise, then jump on a fixed rate if you want to.
Without being too boring, the euro zone crisis is hampering any potential growth here so interest rates look set to stay low for a good while yet, with some economists calling for a 0% bank of england base rate!
I fixed for 5 years a while back before the 2008 credit crunch. It turned out to be a bad move as whilst B.O.E bae rates were cut to record lows, I was stuck with a high monthly repayment whilst others on trackers and SVR's saw their repayment come down by hundreds of pounds per month.
I've recently gone onto a 2yr tracker which tracks at 2.5% above base rate. I'm £200 a month better off.
It's a personal choice, and I'm certainly not a financial adviser. All I'd say is you don't know what's around the corner and 5 yrs is a long time to be tied in to anything.
HTH