org.uk has been generally despised in the past but I have noticed a trend for some UK organizations who used to have the .org switching to org.uk and letting the .org drop (has happened in some other lands as well, typically Australia).
Whilst some of the org.uk names are probably worthless I would suggest that adventure.org.uk is probably one of the better ones.
The UK has a number of facilities for training youth in outdoor skills such as "Outward Bound", "Duke of Edinburgh's Award Scheme" etc and many small council and private run establishments provide such services. This coupled with the opportunity for "Drive a tank" or "Do a curcuit in a formula 1 racing car" as a gift for a friend or loved on means that "adventure" could have good possibilities.
The value is as ever all in finding the right buyer - it's not going to get top $ from a reseller I think.