The Syrian rebels are not a national army who answer to a national government, they are a rabble who have joined force to get rid of Assad after that they will probably start infighting for control of the country. The Syrian economy is smashed and the majority of these rebels will probably have lost everything they own in the world already and so when this conflict ends they are not going to have anything left but these weapons and if a terrorist is willing to give them couple of hundred dollars for an anti aircraft missile they will sell it gift wrapped. When Hamas, Hezbollah or some terrorists in Syria get hold of these weapons and manage to shoot down a military or civilian plane Israel won't be diplomatic instead it will lead to Israel saying gloves off and launching a military campaign like has never been seen before and the result will be alot of arabs being killed. Giving the rebels these weapons is just going to lead to the next regional war and if they are not used against Israel they will be used against Syrian civilians once Assad is gone once they fight for power begins. When the next war breaks out in the region the British will be responsible for making it possible.