Just to add to the above, I am going for my RPL test in the next week, and have 35+ hours at this stage, with 7.5 of that solo.. The comment from my instructor is that is a little under most, with most being around 40-45 hours.
From here there are the 8 Nav exercises to get your PPL, each being several hours long. Plus the obligatory family jaunts and practice.
So 70+ hours would be a reasonable estimate to get to your PPL.
And yes, study at home. I did all self study for the BAK exam, and will do the same for PPL.
The Bob Tait books are very concise, well written, and give you just what you need to get through the exams. The Aviation Theory books go far more in-depth about most systems, and whilst not necessary for the exams, provide great background. I ended up getting both.