From being passed fit to enter, your AFCO will usually email or post the PJFT letter (once the Med Docs are received). It can take a week or two for the AFCO to receive the Med Docs back from the medical examiner, but some AFCOs may take you at your word and email the PJFT letter if you call them. Trouble is, some applicants only hear; "You've passed everything" and miss the "....except we cannot pass you fit until this particular condition is resolved".
PJFT pass to PRMC booking is best discussed with your Careers Adviser upon passing the PRMC. Some people are good to go immediately and can be squeezed onto a PJFT the following week if there's a rush, but most are about a month away unless the applicant wants longer to prepare. Common reasons for delay are phys preps such as inadequate pull-ups or a need to develop swimming technique. Other delays can be through minor injuries, manthrax (flu), booked holidays, work commitments, weight issues, etc.
PRMC pass to entry can usually be achieved in around 4 or 5 weeks on average, but again, can be shorter than that if there's a pressing requirement.