Protest to Stop Western Intervention in Syria
US Embassy Grosvenor Sq London W1A 2LQ
 

The aim of the intervention so far has been to effect regime change, illegal under international law. The solution in Syria cannot lie in further militarising the conflict, or in intervention by Western powers.

It is for the people of the Middle East to decide their own future. The Western powers have a record and history of intervention which has been a key source  of the region's problems. 
As reported by the Observer:

Less than a quarter of the public believes that the government should arm the rebels in Syria, according to a poll in the wake of Britain's support for the lifting of an EU arms embargo.

Just 24% back giving weapons or military supplies to the forces fighting President Bashar al-Assad's army.

...public opinion would not be behind any military intervention, no matter how hands-off. In a sign of the public's changing attitude towards Britain's role in the world, 78% of those polled said that they believe the UK is too overstretched as a result of Iraq and Afghanistan to intervene in a new conflict. Nearly three quarters (72%) believe that the UK can no longer afford to act as a major military power. More than two thirds (69%) believe that the UK should restrict the military to protecting UK territory and providing humanitarian aid in times of crisis.