Well the short answer is – everyone is different. Some people will pick it up fairly quickly and some not so quickly. It also depends on if you have access to another car to practice between lessons.
According to DVSA statistics “those who pass their driving test have had, on average, 47 hours of professional driving training combined with 20 hours of private practice.”
These statistics come from a number of studies undertaken by the Department of Transport. The first study undertaken in the 1988/1989 showed that learner had on average 31 hours with an instructor and 17 private practice giving 48 hours of experience in total. The followup study undertaken in the early 2000s showed 47 hours with an instructor and 20 private practice , or 67 hours in total. The length of the practical test, the manouevers, the road conditions etc have all changed since then (and the test itself has changed slightly since the 2008 study) – The results from the 2008 study are shown below:
Note this is an *average* – some people will take more, some less, it is highly unlikely that you will be at test standard will only 20 hours instruction and no other experience or private practice.