More info (pdf - p12)

2. Subject Access Requests Individuals whose images are recorded have a right of access which usually involves being provided with a copy of the images. These must be provided within 40 days of receiving a request. You may charge a fee of up to £10. Those who request access must provide you with details which allow you to identify them as the subject of the images and also to locate the images on your system.

The Comedian Mark Thomas did something similar years ago.

Basically, they're free to charge up to £10 as an administration fee when you request the footage, which would stop you flooding somebody with requests. It wouldn't stop a thousand organised flashmobbers from all requesting footage from the same people, though.