Most uses of CCTV will be covered by the Data Protection Act. This gives you the right to see information held about you, including CCTV images of you, or images which give away information about you (such as your car number plate).
The Data Protection Act sets rules which CCTV operators must follow when they gather, store and release CCTV images of individuals. The Information Commissioner can enforce these rules. You can see the Information Commissioners Office (iCO) advice to operators in their CCTV code of practice (pdf).
Some uses of CCTV are not covered by the Data Protection Act; for example, the use of cameras for limited household purposes (such as to protect a home from burglary) - even if the camera overlooks the street (for more information in iCO's FAQ).