You won't find a lot of races this end of the year (autumn/winter) taking entries for next year if this year's events haven't happened yet! Most don't even release provisional dates until the upcoming event has happened.
Loads of events are taking entries for Jan-August though, and events like Nottingham open entries the day after. Nottingham is a lovely event by the way, I'd definitely recommend it.
All of the events Cake has mentioned above are good 'uns. White Peak sells out very quickly (I was on the website at midnight to get a place!) but is beautiful and lots of downhill. Worksop is a lovely course, but a bit lumpy. Great medal though
The Longhorn is also lovely, and one of my favourite medals. It may be less muddy next year as they've moved the date.
If you're willing to go down in the Midlands a bit, the Shakespeare half is Stratford Upon Avon (unsurprisingly...) and is a lovely event. Due on the 7th May next year, and entries are open http://www.shakespearemarathon.org.uk/
Have you had a look on Fetcheveryone? Their race listings are usually really good, and you might find some smaller events that aren't well publicised.
I'm sure this was an hour well spent... totting up the scores of runs/swims/rides I've done over the course of the year, not including gym stuff that I haven't recorded. I won't bore the thread with all the details, but lots of swimming (including 1x 11km and 2x 5km OW swims), 11 half marathons, one marathon, a sprint tri and lots of parkruns, among the usual mid-week pootles