This is what happens on the practical driving test day at Goodmayes test centre: Usually your instructor will pick you up about 1 to 1.5 hours before the test and will let you practice all the maneuvers, round abouts, independent driving etc. Its best to be about 10 minutes before the test time. You need to wait in the waiting area which is in the 2nd floor and you can may be drink some water and go to the toilet. At the test slot time, a few examiners will come out in the waiting area and one of them will callout your name. They will ask you to present you provisional licence paper part and the card part. Then they will ask you to read the disclaimer and sign it. Then you will be asked to go down the stairs from the waiting area to the bay parking area where your instructor would have parked the car and you would have already been given the keys of the car. You can choose to take your instructor along with you for the test or go alone. I and most of the guys I know did not take their instructor with them as we thought that will make us nervous.
Now while walking down the stairs to the bay parking, the examiner can ask you to wait in the middle of the first floor and the ground floor and ask you to read the number plate of any vehicle that is appropriately distanced from you. Or, they could ask you to do that while in the bay parking. Once in the bay parking, they would ask you to identify your car and be seated while they note down some details of your car. They get in and sit in the front passenger's seat and ask you if you would like to be briefed about the test. Then they will ask you 2 show me tell me questions. After which they will ask you to drive on out of the bay parking. Now before you leave the bay parking they might ask you to do the pay parking manuver by asking you to get out of the bay, straighten your car and then reverse into one of the free bays. Once out of the bay, they will keep directing you. For example they might say, "Follow the road ahead. Take the 1st road to the left, take the 2nd road to your right, take the road after the bus stop to your right" etc.. There will be one or two independent driving routes given to you. Each route will have about 3 turns. For example, they might say, follow the road, take your 2nd road to your left, at the end of the road turn right, at the traffic lights turn left". So, you need to remember the instructions and drive accordingly. After or before the independent driving, they might ask you to take left or right exits at mini and normal round abouts or let you decide which exits to take by just telling you to follow the signs towards XYZ place. If they don't ask you to do bay parking, they might ask you to do a different manuver like parallel parking, reversing around the corner or turning around the road and sometimes emergency / sudden brake.
During the test, they will ask you to stop the car in a safe place on the left several times. The test lasts for about 40 minutes, during the end of which they hand over to you your passing certificate if you pass or a sheet containing all the major and minor faults committed by you because of which you failed. You might chose to make your instructor available while the examiner briefs you about your faults.