Hey Crumpet, my stepmum had PP with her last 3 pregnancies.

The first one was my stepsister (now almost 17!) which also included the loss of a twin between 7 and 10wks... they told her to have a D&C as they couldn't find the baby on an u/s and the placenta was partially covering the cervix. She refused, and ended up having my stepsister 28 weeks later by C-Section lol

The next one was either a grade 3 or grade 4, I forget exactly it was almost 5 years ago now, but my stepmum had lots of bleeding, especially after a fall in the bath around 16wks that made part of the placenta come away from the uterine wall. She couldnt drive without starting to bleed - something to do with moving her feet/legs to use the break ad accelerator pedals I think. She was ok for short tris as a passenger though.
She also started bleeding t random times for no reason. She was told no driving, no heavy lifting, no other strenuous activities, bed rest for most of the second half of the pregnancy etc, basically the same as wha the others said. My little sister was born via c-sec between 37 and 38 wks.

With her third pregnancy my stepmum was a grade 3, it only covered part of her cervix and my little brother was born via c-sec at 38wks. She had bleeding for most of the pregnancy again as part of the placenta seperated from the uterine wall again, but that was probably due to another fall in the bath.

My stepmum also had the issue of a threatening uterine prolapse (prolapsed uterus?), and was told if she didn't get pregnant with my little sister when she did her uterus would prolapse and she'd have to have a hysterectomy. My little brother was also conceived less than 2 months after my little sister was born as well, so the 2 pregnancies very close together may also have contributed to her PP the third time round. In both those last 2 pregnancies the placenta did move away a bit though, with my little sister it moved 2cm, and with my brother it moved 1.5cm, and though she could have gone for a vaginal birth, she didn't want to risk it or go through the pain of it as she had a bad birth experience with her eldest, my stepbrother (now 22).

Just thought I'd add this just in case it helps a bit

Hopefully the placenta moves away enough that you CAN have the birth you want