Please correct me if I'm wrong but I am under the impression that once you get a council house you effectively get a lifetime tenancy and (provider you can pay the rent) you can stay in that house for life. I am also aware that council house rents are often well below market rates.
This strikes me as very unfair because obviously people's circumstances can change, and one could say, get a substantial pay rise or get married to a higher earning partner who then moves into the council house. I know housing benefit would stop under these circumstances but they'd still be getting a cheap council house when the didn't really need it.