Your ideally placed for a bit of AR in the Lakes. This video should get you inspired...
http://www.dreamteamtelevision.co.uk/view-programmes/adventure-sports/adidas-terrex/
Although most stuff is significantly shorter.
'Expedition AR' is around 3-7 days long and is non-stop. You will have to sleep at some stage, but the clock keeps ticking. Usually race in mixed teams of 4. There are usually transitions where you switch from one discipline to another. Depending on the event, you might have to complete a really long course, or sometimes you can skip some check points (CPs).
As already mentioned, Open Adventure (they are based in the Lakes also) have a selection of events of varying length. This summers main race (the TERREX c2c) is a multi day stage race, so you get an overnight stop each day. Next year there is an expedition race. You can race most of these solo, or in a pair/team.
There are other races around, but I mainly do the Open series as they are based up this way.
Wetherby runner, who are you? Found this post as I noticed you linked to LeedsAR