The rear liners use 1 screw and 4 plastic nuts in each arch - see nuts at #11 here
https://rimmerbros.com/Item--i-GRID001808. The screw goes through the bottom edge of the rear bumper, right behind the road wheel.
Also see
https://the75andztclub.co.uk/forum/s...d.php?t=298371. Note the screw hole bottom left of pic.