British forces in Afghanistan have been having supply (logistical) problems. Fuel needs were underestimated, and addition supplies had to be obtained from Afghan sources. But the biggest problem was spare parts for its wheeled armored vehicles (especially the Mastiff MRAP and the smaller Pinzguaer Vector). Spare parts for helicopters continues to be a problem, although these can be obtained by cannibalizing similar helicopters back in Britain. This, however, meant that fewer helicopters were available for training in Britain.
The armored vehicle parts shortages were largely because the vehicles were being used off road more than anticipated. This caused more wear and tear. The vehicles most affected had been purchased specifically for use in Afghanistan, and there were few other vehicles of the same type, back in Britain, that could be cannibalized for parts.
Cuts in defense spending in Britain also led to low stockpiles of spare parts for many major weapons systems. This was first noticed when, the British AH-64 helicopter gunships first got to Afghanistan and were soon suffering a shortage of spare parts. In reaction to this, hundreds of parts were removed from Britain's AH-64 fleet in order to keep those in Afghanistan in working order. Some British officers would like to get more AH-64s to Afghanistan, but the spare parts situation makes that inadvisable (as it would ground a large number of other AH-64s that were cannibalized.)
The fundamental problem is that Britain has been cutting back on defense spending since the end of the Cold War in 1991, as have most other European countries. But operations in Iraq and Afghanistan have put more helicopters into the air, more often, and in very demanding (hot and dusty) conditions. This has used up spare parts stockpiles, causing many helicopters to be sidelined and often cannibalized for parts, to keep other aircraft in the air. The British military had kept details of this quiet, but it finally got out, and now opposition members of parliament are attempting to force the government to buy more spares and technical services. Now this movement is also supporting efforts to obtain more spares for a wide variety of military gear.