Good context. I knew about ACGS, but only vaguely - but viewers in the UK must have recognized him immediately.
I watched the first few Colin Baker episodes recently. I enjoyed them. For whatever reason, they reverted to a sympathetic (and teasingly dressed) companion with Nicola Bryant, but the actor himself brought some actual character back to the character, despite being saddled with that clown jacket. I enjoyed them though by this time the show's pacing had begun to speed up.
i tried to watch the first Sylvester episode, and cut it after a few minutes of him doing roll-arounds on the floor trying to get away from the Rani. I had read that the show became more pantomine-like towards the end and wonder if this is what is referred to.