I have just put in a team for this same challenge, the Oxfam Trailwalker. You must enter a four man team, and have a support crew during the race, the time allowed has now increased to 30 hours - but I still plan on completing it in under 24.
I'm still injured from the last challenge, my left knee is still very painful when I try to run, my ankle is still weak and now I seem to have a pain in my right heel as well, BUT that's not going to stop me. I'm undergoing physiotherapy and I will get myself back on track to fitness and by July next year I will be fit and raring to go for the next challenge.