There have been so many sorry tales here of up-front payments disappearing when clubs go insolvent or Principals disappear ... hence the above concerns.
But of course there are many totally reputable training organisations for the ATPL (eg Oxford Air Training - though I've no ATPL ambitions)
My logbook says it took me one year and four months to get my PPL, finishing at the age of 43 (15years ago!)
You don't need any prior exams or quaifications. But I found a basic understanding of maths, physics, electrics and the internal combustion engine very helpful. But many others manage very well with a bit more homework.
Go for it! I only wish I'd the drive for the ATPL at 28.
Do it now !
SD