Liverpool City Council has a Landlord Licensing Scheme that all leaseholders who wish to rent out their apartment must register with.

Further details are available from the LCC website:

LCC Landlord Licensing Scheme

Some organisations that will support both tenants and landlords:

ARLA The Association of Residential Lettings Agents

The National Approved Letting Scheme

Residential Landlords Association

Generation Rent 

Articles about renting and tenancies:

London Council Launches Lettings Agency for Private Renters  The Guardian 10.03.16