Not intended to be changed (no mention of it in the first 120,000 miles of the service schedule)... but it can be checked and topped up via a near-impossible to reach (unless you have the car up on a garage car lift) filler/level plug on the front of the gearbox. No good jacking the car to access this as it needs to be sitting level. It can be reached after removing the battery and everything around that - pain!! It can very nearly be reached by jacking front left wheel, removing wheel and the plastic wheel arch liner, then lowering the car to be level again -- measure the height from the road to the top of the wheel arch before jacking and carefully lower back to this height after removing the wheel). The plug unscrews (big Allen key) and is filled until oil just runs out from the filler hole. Note carefully the spec of the oil (in the owner handbook) as its not an 'off the shelf' grade. (Photo shows gearbox on a diesel 4x4 - after removing the undertray - but the fill/level plug is pretty similar on other models too.)