My inferior piloting skills would suggest to me that as you joined downwind, you wouldn't have been 'in the circuit' until the point you joined, therefore any question of illegality is a bit spurious. As long as all your subsequent turns are in the correct direction, I can't see what the issue is.
Unless I'm completely missing something, there is nothing wrong with making a right turn to join downwind for a left hand circuit? I do it every single time I approach my home airfield from the south east and 22 (left hand) is in use.
All this depends on how far out you are, do the right hand turns 5 miles out and you are OK, do them half a mile away and you are not, you might be in your right turn and someone else turning the correct way, you are then both blind to the other aircraft.