Most types of lighting don't require planning permission.
However 'light pollution' is now regarded similarly to noise pollution. i.e. it create a 'nuisance' which the local council (or the individual suffering the nuisance) can seek to remove, using court action if necessary.
This link goes to a page relating to a campaign by astronomers for darker skies. However it considers the law relating to all aspects of light pollution:
http://www.britastro.org/dark-skies/cleanact.h tml?0O
Chris