If you've somehow ended up in the wrong lane, and you don't have the time and space to safely move into the lane you want to be in, go the wrong way.
On your driving test, if you do happen to go the wrong way, you won't get a fault for it, unless you try to go the wrong way up a one way street, or onto a motorway or something. It just counts as a misheard instruction, and the examiner will then modify the test route or ask you to make a couple of turns to get you back on the same route.
In life, forcing your way agressively and late into a different lane is generally considered bad driving. It's generally safer to go the wrong way, then turn around in a side street or something.
This can also be a get out of jail card of sorts.
Here's how:
You're travelling down a street, and have been asked to turn right at the end of the street. You position yourself just to the left of the centre line, but as you get to the give way lines, you realise it's a one way street, and that you should have positioned yourself right over to the right hand side of the road.
At this point, you're failing your test. If you turn right, you'll get a serious fault. And rightly so. It's a dangerous thing to do. You could get someone coming alongside you on your right, and suddenly you're both attempting to emerge side by side into the same bit of road.
The solution is to change your signal, and turn left instead. Your road position is now correct for the manouevre you're undertaking. You will still get a fault marked on your test sheet, but it will be for an incorrect signal on approach. this is generally a minor fault, although it too can sometimes be serious if it adversely affects other road users.
