Cottony Camellia Scale Insect. You can use Bug Clear as a systemic remedy but if you don't have any to hand then perhaps continuing with the gentle rubbing off with a tissue as the shrub doesn't look that big. They do have a waxy coating so a contact insecticide may not work.

Thank you very much ! I think I’ll try to get as many off by hand as I can then spray

Try a little methylated spirits, that dissolves the waxy coating and makes them easier to kill.

Thank you for the mentholated spirit suggestion - the white coating does make rubbing them off hard work!