It takes as long as it takes, some people it takes 5 minutes god knows how and others it takes longer. I took me 40 lessons, i didnt feel ready until around 30, id rather that then booling in to your test early when you arent ready and failing it as its just more stress and £. How people passed after 15-20 lessons is beyond me unless you have driven before. Yes its expansive but once its done then it gets even more ludicrous. The cost of driving is immense if you like your cars. Good luck anyway.