Is it really standard practice in the UK to teach that the turn onto downwind occurs after reaching circuit height?
If so, no wonder some circuits are large considering the performance of some a/c when heavy &/or on a hot day (Yeah, yeah, I know it's the UK, I just threw in the Temp. thing for accuracy...
)
Can't see the necessity for it, myself.
Oz & US both tend to the procedure of turning onto d/wind at a point that will give you an appropriate spacing. If circuit is not yet achieved then continue the climb during the turn & on d/wind.
Oz also prohibits the first turn after t/off until 500' and requires final to commence a minimum of 500m from the AD boundary although these rules are rarely significant factor. The 500' turn is probably the more significant of the two since it sets the starting height for X/wind.