Can shop or betting workers forfeit their protected status?

Yes. If protected shop or betting workers give their employer a written, signed and dated opting-in notice in which they expressly state that they wish to work on Sundays or that they do not object to Sunday working, and then expressly agree with their employer to do shop work or betting work on Sundays or on a particular Sunday, they will lose their protected status.

They can, however, later serve an opting-out notice on their employer, if they no longer wish to work on Sundays.