As it is for a PPL, it does not need to be through an ATO (more expensive!), a DTO (cheaper!) will be sufficient.
If you have passed ATPL exams (which you have) I would be very, very surprised if you had to resit any PPL exams. I know that anyone doing an IMC Rating course does not have to sit the IMC Rating exam if they have passed ATPL exams.
I suspect that you would only have to do a few exercises to fill the 'missing bits'. You already have the SEP hours, both dual and solo, but may be a bit short on some aspects, such as, have you done the 'Solo Qualifying Cross Country'.
etc.? You would, of course, have to pass the PPL flight test.
The end goal is to get a PPL and fly recreationally to keep my airmanship and flying skills sharp.
Good luck and
enjoy it!