I believe there are some big charity run events but you would probably get more out of it if you could persuade someone to do it as a minibus drive, in addition a minibus is likely to be quicker as with a coach no only will you travel slower around the hills but also you will have the problem of waiting for other groups to finish each hill before moving on to the next.
The three peaks yacht race is now in its 25th year and is a serious event "389 sea miles sailing, 30 miles cycling, and 59 miles of walking"