The general rule is that you can't hold award seats. So it is really up to how you perceive the risk of the award seat disappearing by the 1st of November.

However I do wonder what will happen in the following case - you call them and book the flights. Ticketing will not happen until after 1 November (not unlikely due to the normal ticketing delays, but you can't count on it either). Will they charge you the new lower fuel surcharge or the current one in that case?

I guess the saving is less than £25, otherwise you could book now, and cancel and re-book after 1 November if award seats are still available.