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.”
The DVSA undertook a study some years ago asking a selection of learners to complete a diary and record how many hours with an instructor and how many hours private practice they did, the results for those that passed the test are in column two of the table below.
(Mean is the normal average)
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.