excuses against intervention, the Brit. one (echoed by you) of not intervening because of the possible political implications of who will replace Assad,

As I have told you many times, that is not true.
It is a lie Jim.

Britain has made no excuse for not intervening, and I have not echoed any.
It has made a large number of interventions.
The British position is that Assad must go.
Assad is still in power thanks only to the support of Russia, China and Iran.