Can non-protected shop or betting workers opt out of Sunday working?

Yes. Shop and betting workers who are not protected, or those who have forfeited their protected status, have the right to opt out of Sunday working, so long as they are not employed to work only on Sundays. To exercise that right, they must give their employer at least three months' advance notice, in writing, of their intention to stop working on Sundays.

A protected worker is generally one who has been employed since before the relevant Sunday trading legislation came into force, or who cannot be required to work on Sundays under their contract.