Here is a list of useful 'random' links I found so far that cover different aspects of the business :
(To be continuously updated)
https://www.equity.org.uk/jobs-career/starting-out/so-you-want-to-be-a-performer/
http://www.actorsactingtips.co.uk/2010/05/24/top-10-resting-jobs-for-actors/
http://talent.castingnetworks.co.uk/Common/Resources.aspx
http://www.guardian.co.uk/stage/theatreblog
http://www.londontheatreblog.co.uk/a-practical-guide-to-theatre-and-the-web-facebook/
http://www.londontheatreblog.co.uk/a-practical-guide-to-theatre-and-the-web-twitter/