Copper to plastic in confined space.

[Dylan123]

Hi. Remodelling my bathroom. It's necessary to join my 22mm plastic to 22mm copper in restricted space in the ceiling just outside the bathroom. Finding it very difficult to get the hand room to be able to properly fit a push fit coupling. Can I use compression? Any particular type?
Also, about a foot downstream of this coupling pipe has to take a 90 degree downward turn. I'm nervous about using an elbow as, once finished, it will be completely inaccessible. Is there any kind of 22mm pipe that would be flexible enough to make this turn? There is room to make the turn quite gently.

Thanks from a diyer!