@chopera: Landlords do not throw the tenants out on a whim. A good tenant is as hard to find as a good employee. (I know it very rear in Spain for a employer to realise the benefits of good employee & help them to develop and get the synergy going ).
The Landlord only does this where his/her circumstances changes i.e. job relocation, divorce, children needing housing near university/work or the tenants have been a disruptive to the others.
In UK the Landlord has the obligation/responsibility as to how his/her tenants behave