Don't forget to factor in remortgage fees in two years if you go for that deal. That'll be another £999 or whatever lenders are charging for product fees now. Plus the solicitors paperwork that will be required if you switch lender.
Ooooo - that's a very good point. In general our mortgage broker is excellent... but he does like to keep us on a revolving remortgage train every couple of years. Whilst that's suited us well in the past, we're now borrowing more money to do a loft conversion and I think it's time we locked in for a longer deal.