Notches around the edges of the leaves could be vine weevil. Holes might also be birds pecking the plants to get at the flower buds - they love them. Slugs and snails generally leave primroses alone, in my experience, and so do rabbits.

if find the small keeled slugs eat the primulas so you are lucky landgirl. I also noticed small green caterpillars on them today when I finally got outside to do some weeding.