To be frank, the current British Driving Licence does not test you on real world stuff, most of the test is done at 30mph! You still have to shuffle the wheel for christ sakes!
I'm not saying anyone who passes the test is instantly the worlds most amazing driver, but anyone who has had NO formal tuition at all is... dangerous on the road to say the least.
If you don't understand things like roundabout lane disciplines, it's gonna get ugly.
EDIT - The test checks that you are competent to drive - it's limited to what you can get done in 45 mins, but if it was that rubbish then surely everyone would pass straight away...