A handful of publishers are responsible for nearly all London's local newspapers. The best paper to approach with your project when looking for local coverage are the one's serving the local area the project is happening in - and the best way to find that one is to go to your local newsagents.
You can find a comprehensive listing of national, general and specialist interest magazines on Newsstand:
Visual and contemporary arts
Crafts and design
Photogaphy and lens based interest
Cultural theory / interest (includes performance / live art)
An excellent listing of UK national newspapers is at PaperBoy's UK site.