Your guess will be as good as anyone elses's regarding where rates will be in 3 years but many bonds will let you withdraw money in an emergency (perhaps not if you find a better interest rate though) subject to loss of some interest. It is worth checking the small print for the bonds that you are looking at but, personally, I would prefer the lower interest rate with the option to get at the money if it is needed.

I have £20000 that I could afford to put away in a 5.30% fixed rate savings bond for 5 years. The 5 yr fixed bonds do though all appear to have no withdrawal or closure permitted during the term should the interest rates go substantially above 5%. The question is should I do that or should I opt for a shorter term bond, say 4%+ over three years with a 90 day interest penalty.