If you have a driving test in one hour's time what can you do to increase your chances of passing? Well not alot, especially if you are not fully prepared. As a DSA approved instructor, the last hour before a practical car assessment is usually spent with the learner driving around the local test centre area routes, getting used to the traffic and weather conditions, I would normally go over the least favorite driving maneuver, just to brush up on the skills, but this is not the time to be teaching new ways of doing things.
I also use the last hour before getting to the dsa centre to boost the candidate's confidence, reminding them that they've got all the skills and experience required to get that desired pass certificate, and all they've got to do is to drive to the best of their ability as they have been doing on thier driving lessons. If they make a mistake, they should not give up, but continue until the very end.
If there is any local hotspot that can be tricky on the driving test, then I would also take them there if there is enough time during the final one hour (this wouldn't be the first time of going there, but it would just be to have an idea what conditions are like prior to the test), though things could obviously change by the time the candidate gets there with the dsa examiner.
If you are not going to the driving test with an instructor, then you need to get to the test centre area early, and drive round with you supervisor, also check the car over throughl to make sure it meets the DSA test requirements (tyres, lights, windscreen) as you don't want to lose your fee and the opportunity of getting a full british driving licence due to bald tyres or headlights not working. You don't have much time in the last hour before the test to visit a garage or change a flat tyre especially if you are not familiar with the test centre area.
Finally make sure you arrive at the centre around 15 minutes before your test so you car do the bay parking exercise. The closer to your appoinment you arrive, the busier the car park will be, and you don't want unnecessary pressure at this time, so in a nutshell make valuable use of the one hour before your UK driving test, but above all remain calm and focus on the task at hand, if you've prepared for it, then you can do it.