It is disappointing (to say the least) to see how far removed British political thinking is from the wisdom necessary to address this dilemma.
The answer (if one is to get involved at all) lies in neither with backing the rebels or the current regime but in removing both, installing a provisional government (purely administrative) made up, if necessary, by foreign (even British) administrators supervising local personnel, while creating a domestic environment in which independent parties can be formed and fair elections held. But, that is a 5 year plan at the least.
My advice is that unless you are willing to do the above - stay out of it.