No offence meant bemused, just a little bemusement of my own.
(Quick disclaimer, whilst I've a lot of GA hours in the UK and elsewhere, I'm a quite inexperienced instructor, so won't be offended by more experienced instructors who care to disagree.)
With civil flying students there are many right ways, and many wrong ways of flying. The trick is to make sure that they are doing it "a right way", and not to get anally retentive about "not my way".
At most civil airports, the 3D shape of the circuit (apart from the climb and descent angles) is generally not negotiable - apart from some small variations (depending upon local preferences, extending downwind or orbiting). The downwind call position is fixed - apart from variations to suit other radio traffic.
But yes - it's nominally rectangular (with local shape variations), some debate about angle of bank in the turns: I'd personally use about 10-15 degrees in the climb or level, 15-25 degrees descending - speeds and flap settings to fit into other traffic and suit the aeroplane, angle and power on the descent to do the same (and also many of us prefer a low power steep approach if landing over somewhere you can't land - for example over High Wycombe into 24 at Booker). Microlights and homebuilts may often fly idle approaches as a matter of course (a mentality brought on by uncertified engines), creating particularly steep approach angles.
G