We're in a similar situation - 5 year fixed ends in May. Our exit fee is £11,600! (unlike some other banks who may lower the exit fee over time - so you pay less to exit with one year to go, than you would for four, for example - Santander is known to keeping their exit fees high. Definitely a lesson learned moving forward - exit fees will be one of the main things I consider from now on, when foxing.)
We spoke to a mortgage broker back in July, and he did the sums, and advised us to not fix then. With the high exit fee, and what the new mortgage payments would have been (higher percentage than we currently have, obviously), it just did;t make sense - he advised we saved the difference - which we have been doing since July (least it's going into our savings, rather than interest to a bank).
He also said that (at that time) banks were offering higher percentages than the BoE was rising the interest (so a lot more than beyond the 1% higher than BoE rate) - supply and demand. Lots of houses being sold at the time, meaning more mortgages being taken out, and lots of people were panicking and looking to remortgage earlier than expected (as we had). He expected it soon to filter down, as less mortgages were being taken out (which yea, I know will be cancelled out by BoE rises before then, but in theory means we'd be looking at similar percentages as we had in July).
He also said we can arrange a fix up to 6 months in advance - get it agreed etc, but see how the interest rates/new deals go in those 6 months. So we're meeting with him in November, and will lock in a rate then, but come April next year, if we get a better interest deal then - we'll take the new deal. A decent broker should be able to do the same for you around December.