Britons Joining Jihad Stripped Of NationalitySky News just had one of these jihadis on, who explained that he had no interest in fighting any jihad in Britain, that he and his comrades were there to help the Syrian people by overthrowing Assad. It's really quite simple. Then the woman from the Royal United Services Institute explained that it is all very complicated, that there are at least 200 Britons fighting in Syria, and they might come back, sit around for a couple of years, and then Boom!
The Left has tended to go along with the security experts and the government, in seeing stopping intervention in Syria as more important than overthrowing Assad. Tom White puts more extremely in the comments, "if they are prepared to fight for Islam they have no place in our country." There was a demonstration in support of the Syrian revolution in London on Saturday, I don't think there was anyone from the Left on it. There is a worldwide day of action for Syria on Saturday 11th January, I would hope that my fellow socialists had got off their arse by then. It is the lack of help for Syrians that drives some of them into the hands of the al-Qaida elements (some of them are secular enough that that's never going to happen, though their hatred of the West and the Left that have done nothing to help might still be quite intense), it is Assad who let many of them out of prison to derail the revolution, and his forces don't bomb their headquarters in Raqqa.
A couple of friends have recently travelled to help refugees (foreign fighters generally aren't welcomed that much, Syrians need anti-aircraft weapons to stop the aerial bombardment more than soldiers) and have been heavily questioned at airports. It has generally been assumed that this is just to find out if they know any jihadis, but it might be that anyone who helps the Syrian people is under threat from Western governments.