The independent driving test usually lasts around 10 minutes. In this part of the test, you will have to follow the direction of the sat nav not the direction of the examiner. This makes the test last longer to around 20 minutes (this is usually roughly half of the test).

During most of the independent driving, most candidates will be asked to follow the direction of the sat nav.

The part people worry about is whether they need to set their own route. Well, you don't have to because the examiner will provide the direction and set it up. So, it doesn't really matter what sat nav model you used or practice with cause a route is a route. 

Others ask whether they can use their own direction from the sat nav. The answer to this question is no, you must use the direction that has been provided by your examiner.

You are able to ask the examiner for confirmation of where you're going if you're not sure. This will not affect your result. It doesn't matter if you go the wrong way, but if you make a fault while doing so then this will affect your result.