Nearly everybody loses marks in the same few places, and none of them are about driving badly.
We have been running mock tests in the same way for four years, marked by an instructor who has not taught the person, on a copy of the sheet an examiner uses. The sheets are remarkably similar.
Mirrors before signalling, not after. This is the most common mark by a distance and it is a habit rather than a skill. The examiner is watching your eyes and your head, and a glance you did not take is a glance they can see you did not take.
Stopping too far from the line at a junction, so you cannot actually see, and then creeping. One firm stop where you can see beats two tentative ones.
Speed on the straight between the mosque and the school, where nearly everybody drifts to forty because the road is wide and empty. Empty is not permission.
Not looking into the road you are turning into. People look at the corner they are avoiding rather than the space they are going into, which is also why the turn ends up wide.
Hands off the wheel to shift, on an automatic, out of nervousness. Examiners mark it and nobody knows they are doing it.
And the one we see every week: a perfectly good drive with one late decision at the roundabout at the end, taken while thinking about the drive rather than the roundabout. The last four minutes of a test are where most of the marks go.
None of this is about driving badly. All of it is about doing visibly what you are already doing invisibly, which is the actual skill a test measures. That is why a mock test marked by somebody who has never taught you is worth more than four extra lessons with somebody who has.