Doing my retest soon due to my instructor not teaching me the 100% correct method in the reverse technique 
Just want to clarify;
i know to park on the left with the cone beside my wheel. when you start to reverse you need to go dead slow and get full lock anticlockwise. How then do you avoid crossing the yellow line on your right with your tyre? I crossed the line and failed when I did this initially.
Am i meant to get full lock for a little while and then straighten it up a bit?
Iām ok with every other part of the reverse, just a bit lost on avoiding the yellow line.
Definitely stating to panic a bit. I passed the actual drive part, quite unhappy Iām back doing this again to get the pass.
Doesnāt sound like a good instructor to me!
This is the basics, he should have made sure you understood this and what is required before your test!
Iām about to go through the same in the next 2 or 3 weeks. You can be sure that Iāll have it nailed in training as I will ask if itās not clear.
Poor show from your instructor.
I very much agree I assure youā¦
Open window and look down then adjust steering as necessary to avoid going over the line
If you need the back to kick out more to avoid cone B then run the wheel along the line a little more
Dont forget to split your view between looking down and in your mirrors
Your instructor should really have covered this with you 
O the joys of working in an unregulated industry well populated with incompetent āinstructorsā!
Firstly, get your start position correct. The examiner should be able to stand at the cone nearest your front nearside and look across the front to the other cone. Then he should be able to repeat this, looking up the side of the truck to the centre (B) cone. Iām concerned that you say you stop with the cone beside your wheel. This isnāt correct.
Most CAT C trucks (feel free to tell me what make/model/length yours is) will happily clear the centre (B) cone if you steer 1 and a half turns to the left. If youāre positioned correctly when you start, youāll easily miss the yellow line on your right. But, as ROG has suggested, wind the window down and have a look. Or you can often see your tyre clearly in the wide angle mirror (handy if itās raining!). But if itās getting precariously close to the line, just steer the other way a bit ie right. Get it safely away from the line but then steer left again otherwise B cone will creep under your truck.
Hope this helps. Itās a scandal that some āinstructorsā are taking money from innocent victims and then not supplying a correctly marked reversing area - let alone correct instruction.
Best of luck with it.
Pete 
Thanks Peter, the instructor was highly recommended locally, but iāve had a very poor experience. Iāll not be doing any further training with them.
Best tip my instructor gave me was to dry steer to a full left lock before releasing the handbrake and moving. Then it was all about keeping it slow and controlled working inside the yellow line as ROG and Peter say above.
If you are referring to a Class 2 test here is a tip.
When you position your truck try to get close to the nearside cone with your bumper, but not close enough to touch it.
Making sure you are close to the two cones but not actually between them.
Then put full left hand lock on before you begin to move, as said above take it slowly, open your window and look down at the tyre then reverse slowly and make your tyre follow the yellow line, but not over it.
Check your mirrors and when you see the cone at the end of the box come into view begin to wind your lock off taking care not to drive over the yellow line then concentrate on the cone and reverse into the box.
If you line your truck up at the correct spot on the yellow line in the box before the test, sit in the drivers seat and check where the line of sight in the mirror puts your rear mudguard, you might find it gives you a point of reference where your truck should be and the actual line.
You then only need to concentrate on putting your truck in the same position and not have to worry about guessing where the line is.
Best of luck.
try to get close to the offside (drivers side) cone with your bumper,
I think you mean nearside (passenger side). Otherwise youāll immediately run onto the yellow line on your right.
Pete
That is the thing, there isnāt a 100% correct method. The rules were made up and then instructors and learners decide on the best way to tackle it to give the best chance of a pass. The parameters include that there is usually limited practice time.
The left lock approach attempts to guarantee you get round cone B and in theory it should give you plenty of room for the second part of the reverse.
As other posters have said, take the lock off when you get close to the line, but keep the left on to keep the tyre parallel with the line. You will start to come naturally away from the line, but keep an eye on where you are going too.
Got the pass on the retest, thanks all for the advice 
