This manager seems not to have a clue about security of information, so:-
1. If they are a limited company you can find out the names of directors (for a small fee) from the Companies House website, and then write a formal complaint letter to them.
2. Even if they are not a limited co. they must be owned by someone - presumably not the manager. If you can find out who, write to them.
3. The credit card companies ought to be interested in taking this up with them, as it is a practice that could easily lead to card fraud. You could contact the fraud prevention people at your credit card company and ask if they can do anything about it. (You ought to contact them anyway, just in case your details have been mis-appropriated as a result of this.)