Tempted to sign up for a marathon to do one of my 42K training runs. Can't imagine doing that sort of distance and it not officially counting towards how many marathons I've done. I am a bit event / race obsessed though. Would have to make sure I didn't get carried away and just plod round.
It's not at midnight, but the Nos Galan races in Mountain Ash, South Wales are on the evening of New Years Eve and normally sell out every year. Kids race, Elite Race, Fireworks and then the main 5k fun run to finish.
Entered for my first Ultra next April - Vale Coastal Ultra 32 miler so roughly 50K. Probably qualifies as reasonably flat in the Ultra world although there are a couple of inclines towards the end. Seems quite beginner friendly with a very generous time limit.
Training for Snowdon marathon in October so like DoubleOhDave it'll probably be a case of keeping the mileage up for the 5 months in between. Looked at a couple of training plans which seem a little bit scary. My aim (as I'm sure it is for 99.9% of first time Ultra runners) is to just get round.