There is no time limit to complete the PPL I believe, your exams however do. All but the RT have a limit, you have 18 months to complete all exams (again excluding RT). Once you have completed this then you have 2 years to finish the PPL. Mine timed out once, so I had to re-take all but passed all of them first time x2 so no fails. I would say about 2 years if average if you’re flying a few times a month, depends on the weather.