I'm signed up to do a first triathlon in June and will be following up with Tough Mudder in July.
It's a sprint 750m swim, 19.8km bike, 5.7km run at Blenheim Palace.
http://www.theblenheimtriathlon.com/
Tough Mudder events are hardcore 10-12 mile (18-20 km) obstacle course challenges designed to test your all-around strength, stamina, mental grit and camaraderie. With the most innovative obstacles and over one million participants globally to date, Tough Mudder is the premier obstacle course series in the world.
http://toughmudder.com/obstacles
For example - http://toughmudder.co.uk/content/electroshock-therapy-0
The charity
http://localgiving.com/charity/heartofexperiancharityfund