I think fixed rate can make sense in some circumstances, but you need to factor in the expectation of eventually refinancing. But then frankly you should expect to refinance anyway. It's highly unlikely that the same mortgage will turn out to be just a suitable to your circumstances and the competitive landscape in 20 years time as it is now, or even in 10 years, whatever mortgage you choose.

Here's my (partial) heuristic. If you see adverts on TV for fixed rate mortgages, don't get one.