As above we went for 5 year so we knew what we'd be paying for that period with no unknowns. Worked against us in the long run as we've been tied into a 5.29% rate for 4 years now with another to go but you roll the dice to takes you chances... Will probably be a bit less risk averse this time round but I'm also not up for paying £995 fees every couple of years to go to a new product!!
Edit: over 20 years repayment and we've been overpaying a bit on the way through to take that period down a touch.