sometimes its better to just keeep 

I'm veering towards the five year fixed, on the basis that there's only likely to be at max a cut of 0.4% in the BOE base rate and things are more likely to go sh*t-shaped and interest rates head north in the 3-5 year range..... although that's nearly a reason to go 2 year fixed and review at that point.... but what if things are on the skids at that point and rates are rising already?
Could things change that fast, that badly?

how do you know what the uk economy is going to do over the next 5 years. you cannot judge by whats happened in the past. you cannot trust what the house of lords say as they lie, and decieve.
The only thing you'll see crystal ball gazing is a load of crystal balls as a mentor once sagely told me. History can teach us a lot though.... provided you're able to deliver some interpretation rather than just looking going 'yeah stuff happened, innit'.
I am curious about the comment about the House of Lords. It's like saying 'you cannot judge by whats happened in the past. you cannot trust the department of education.' Makes about as much sense in this context..... or does it? Can you enlighten us?