I've done this 3 times in a year, so listen up and learn from my mistakes!
Attempt 1:
Paid a guy to re-trim my pillars and headlining, 60 quid, bargain! The guy used the wrong glue and it peeled and sagged within weeks.
Attempt 2:
I pulled all the sagging material off and applied my own but due to guy in attempt one removing the good old grey fabric, my glue had nothing to stick to, after a few weeks, again it all sagged and peeled within weeks.
Attemp 3:
I got really f**ked off, pulled everything out. Went down the scrappy and got new headliner and pillars.
Cleaned the pillars with white spirit and scrubbed them with a scotch pad (gives the glue something to stick to) I used faux black leather on my pillars and sunroof slide. I bought black grab handles and visors from a guy off here. I rattle canned the bits of platic in the pillars where the seat belts come from (be careful excess glue doesn't get on them or the won't move, ooops lol) rattle canned the interior light console and the piece that goes over my sunroof motor, also rattle canned my whole headliner, took a while as it's fabric and it absorbed some of the paint, just kept adding layers till it was all even and looked good (I applied 2 layers of primer, 2 layers of paint then 2 layers of clear laquer to the plastic parts) Once all dry and ready, bibbety bobbety boo the car was done lol (took weeks as I was working and disheartened from being f**ked over in attempt 1 and 2)