Now then Jim - let's take the ammunition you said was sold to Assad's regime by the UK and used to kill people in Homs in 2012.

Your version is based on part of a newspaper article in the Daily Mail, and that was basically that. You failed to comment on the fact stated in the article you linked to that the British Government had sold nothing, what they had done was issue a private arms dealer an export licence for NATO 7.62x51mm small arms ammunition in 2009. Further digging identified the value of this licence at £30,000.

Now how do you go on about proving that an export licence wasn't used?

Some indicators would be that:

1: The Daily Mail article would have mentioned that £30,000 worth of 7.62mm ammo had been delivered - It didn't

2: The ammunition itself would be of no use whatsoever to the Syrian Police or Armed Forces who use Russian weapons that use 7.62x39mm ammunition, standard NATO 7.62x51mm Ammunition would be 12mm too long so it could not be fired.

3: Even in the unlikely event that this unusable ammunition was delivered, that delivery would have been in 2009, £30,000 buys in military terms a minute quantity of ammunition that certainly would not have still been around in 2012 to kill people in Homs (The only way the Syrian Armed Forces or police could have killed people with this ammunition would be if they dropped the boxes of it on people's heads)

Taking all of that into account, logically I would say that the ammo was never delivered. A newspaper article talking about an export licence being granted does not equate to proof that anything was delivered.