Brian Reade in the Daily Mirror summed it up perfectly for me the other day.

Al-Qaeda are one of the rebel groups that are trying to force Assad out, so if Britain intervened, we would effectively be working alongside Al-Qaeda, whilst at the same time bombing them in Afghanistan. How on earth do you explain that one?

I'm pleased common sense has prevailed and we're not taking military action. Why should we even get involved? We should only get involved if Assad started threatening to attack us instead of his own civilians. Let's make it absolutely clear though that I am totally against what he's doing.