UN weapons inspectors report to the UN Security Council has come out with the facts relating to the attack on the 21st August:

1: The weaponised agent used was Sarin
2: It was delivered by Rockets that had been fired into the area in question (Sorry Akenaton there goes your leak from stored weapons theory)
3: Via forensic examination of the site, the prevailing weather at the time of the attack and determination of the trajectories of the missiles fired, they came from areas controlled by Assad's forces
4: Examination of the projectiles indicated that one had writing in cyrillic script (What was the caption Jom? - From Russia with Love?).

The UN inspectors did complete their work in Syria, the UN, true to form, sent them into Syria to do a non-job, find out if chemical weapons had been used, but make absolutely no attempt to apportion blame for the attack - useless as always.