holy cow that looks complicated ... but it just may be that i don't know one word french :P
When i taught my students (in the US) i'd give them lots of practice and just work off the 'feel' method. Give them basic guidelines as to when to turn and just let them try until they get it. ALthough i can see that racking up costs in the EU with all those landing fees.
Generally it comes down to letting them know to always turn early on downwind, usually after passing the end of the runway and 1/2mile lateral distance. While turning keep the turn at such a rate that the wingtip is touching the end of the runway (roughly 25degrees?) - while keeping the speed ad the recommended glidespeed. Assess what the wind is doing to you on base (how fast you're getting pushed, so you can decide when to turn to the numbers). Once decision is made to turn to numbers/runway make corrections for altitude by using a multitude of methods - flaps + forward slip for drag, or adjustand ground track to runway, if those don't deliver the desired results you can "dive" for a point before the runway/desired touch down point. This increases speed but also drag which will make you lose energy so when you level out again your at a lower altitude with less energy.
Reason i teach to always turn early is 'cause you can always correct for being to high, but never for being to low. I used the same method to teach Power off 180's where u have to hit a 100ft target (dunno if you guys do that in the EU?). It worked for all my students quite well and not one of them ever failed a stagecheck/checkride.