Where can I find a Database of British Theatre Actors of the 20th Century?

Question:

Where can I find a Database of British Theatre Actors of the 20th Century?

Hello!
I am looking for a database or listing of British theatre actors of teh 20th century, possibly including minor actors as well.

My best guess was to use www.imdb.com and to find those having played in films.

Perhaps do you know anything that is not in imdb (thus for theatre) for such actors as
John Lothar,
Richard Nelson,
John Mannell,
John Barrett,
Sheila Sinclair
Jenny Trafford.

They are supposed to be actors of the 30's until 60's...

Best Answer - Chosen by Asker: Maybe at the library they would have a book on it, look it up on an internet search engine too!