What Dez said, rollback counts as loss of control = insta fail, they're super harsh on it. If it's only an inch or two and under certain conditions they can turn a blind eye but if it's as a result of a stall they have to count it. Best advice is be aware of your surroundings, if your being asked to take off from even a slight incline, bite the clutch right in with extra gas before taking the handbrake off, get the car rattling and creaking to go, the examiner will understand why your doing it.
I'd be a bit curious about your mate passing with 6 identical minors though, as that's obv a fail? like did it say 6 on the form or was the examiner using discretion? In any case any complaint to DVLA along the line of 'But my mate...' won't go anywhere.