I've never ran a race before other than Park Runs but have ran about 1300km per year for the last three years, and ran 50km on my own several times fairly comfortably (including Welsh 3000s and around Bleaklow/Kinder), as well as marathon distances. So I know I can do the distance on the terrain in the time required.
Perhaps it could be fun to enter an organised ultra in the Peak District... I can see there are several in September like the ones listed below. What should I be thinking of when picking...? I'm not competitive... is the race just for the camaraderie and so on? I think I'd be quite nervous with all the build up on the morning and the checking of kit etc., and starting with a crowd. The minimum kit list is more than I would normally carry (map, compass, emergency bag, first aid kit etc. would all be extra, don't judge me. But I suppose you can carry less food if there are check-points).
The Peak Running 33
High Peak 70/100km RangerUltras
Edale MRT Nine Edges
Ultra X 110km (whole weekend thing)
Peak District South and North 43/50/93km RangerUltras