I thought it might be worth having a thread devoted to shorter trail races, and other events, that we use as part of our training regime for ultras.
I think that it is in any ultra runners interests to participate in trail races of all lengths, that fall within their home county, because this will greatly expand their body of local knowledge. I am currently based in Leicestershire, and I have integrated parts of a number of local races into my training runs:
The Woodhouse Challenge is a hilly local 13.5 mile trail race. It can be expanded to 18, or 20 miles by adding bits, to make the length of training run that you want. Or if you really want a beasting, you can do two circuits of the course.
The Easter Bunny 10k is a rather hilly local 10k,and by running multiple laps of the course, you can obtain a pretty beastly hill training session.
Longer local trail races that I sometimes do in place of my LSR include the Belvoir Challenge, the Charnwood Marathon, and the Seagrave Wolds Challenge.
While trail races make the best preparation for the kind of events we do, there is no reason why road races, or even obstacle races cannot form a useful part of your preparations.