I also find it odd that we have to test a rejected take-off when it was not a mandatory part of the original PPL, though the examiner could chose to include it inder section 5d.
My method of ensuring an element of surprise is to telephone the tower prior to taxying and let them know what is going on. Puzzles the candidate occasionally when the tower wont let him/her 'takeoff' with what would normally be adequate spacing.