There was talk in the newspapers about an appeal to the European Court over speed cameras. It was questioning whether vehicle owners should be forced to disclose the identity of a driver prosecuted for speeding. What was the outcome?
The existing law is that it is not an infringement of the Human Rights Act to require this information. You are obliged to supply the information or run the risk of being prosecuted for failing to do so. If you can reasonably argue that you have no way of knowing who was driving at the time you should give that information to the police to allow them to conduct their enquiries. If the matter becomes too complex at any stage you should consult a solicitor.