There is a site out there called the London Advertising Directory. This site is very easy to find things and extremely easy to search for things. They have over 900 links and over 50 categories in many areas of interest such as marketing, agencies, and photography to just name a few.
Check them out and decide for yourself if this is something that could help you. And while you are there you can suggest a category or suggest a link. There are also random links, top links and popular links you can view also.
Be Aware that ALL links in posts are paid/sponsored by the company Blogitive
READ DISCLOSURE in compliance with the FTC