WW2 Black troops in Britain

Hello, I am a bit desperate looking for information about WW2 Black troops in Britain.

It can be lists of personnel, photos, articles, any type of record that gives us a bit to go on, because we are very depressed after several months looking for info.

Whenever it seems that we have found something, there is just a code and no text.

If we research the code, we get the 'not found' message, like in https://www.archives.gov/files/publications/ref-info-papers/rip105.pdf.

Please, if anyone can share something or have an indication, reply to this post.

Thank you very much.