This rears it's head occassionally and I have put together this 1 page document that might clear up a few of the definitions/relationships.
http://bit.ly/12OQccB
Edit - I have added a second page to cover subtenancies created via agents under 'guaranteed rent' schemes where the agent is the tenant.
http://bit.ly/12OQccB
Edit - I have added a second page to cover subtenancies created via agents under 'guaranteed rent' schemes where the agent is the tenant.