Aircraft shouldn't overtake others in the circuit, and aircraft leaving the circuit should either climb straight ahead out of the circuit, or follow the circuit around until they are facing the direction they want to go.
Next time I'm in a twin on the downwind leg and I come across a flexwing microlight immediately in front of me, I'll remember not to overtake.
And next time I'm in an empty circuit with time to waste and fuel to burn I'll keep going round in circles.