Independent driving was introduced in October 2010 and has seen some changes over the years which of now includes the satnav. 4 out of 5 test will be done with the satnav, if you have the older version it will still be around 20 minutes long.
Satnav version: The examiner will ask you to pull over, put a dash pad (rubber grippy one) on the dash, the satnav unit will have a powerbank on it so it won't need plugging in. The examiner will select the route for you to follow (the TomTom Start 52 allows routes to be recorded), you do not need to do anything. The examiner will then ask you drive for a short period following directions from the satnav, you may have to answer the Show Me question during this time as well as do the reversing exercise. If you go wrong the satnav will direct you back onto the route, how easy is that? You do have to look at road markings, roadsigns and obey the rules.
Non satnav version: again the examiner asks you to pull up at the side of the road and you'll be driving for a short distance recieving minimal instruction. There are three versions, you'll have one of them: verbal, verbal & roadsign and roadsign only.
Verbal: "Turn left at the end of the road, at the first roundabout follow the road ahead and at the second roundabout turn left. Then pull up in a safe place.
Verbal & roadsign: "Turn left at the end of the road and follow the signs for Shenley Brook End."
Roadsign only: "Follow the signs for Northampton. Now follow the signs for Central Milton Keynes."
Some important bits of advice:
1) you aren't following the signs to, you don't actually drive there, just follow the signs for that general direction.
2) don't change lanes unless you know where you're going, you may need to change back.
3) if you can't see a roadsign, keep following the road ahead. If the sign is missing the examiner may advise you where to go.
4) going the wrong way if not an issue as long as you do it correctly and don't drive slowly trying to fix it, the examiner may offer advice. However, if you accidentally go down the A5, it won't be a quick fix. Not as though you can just turn around.