Look out for online discounts with Intrepid Travel
IntrepidTravel often have up to 15% of their trips that are not selling very well and it is well worth keeping an eye out for the adventure holidays.
Intrepid are based in Australia but cover the whoe planet and have offices in the UK and other locations.
Look at the specific holidays and then check out the costs and dates link. This is where you will find the 15% discounts.