its not true privatisation, nor is it truly under state control.
The operators are close to privatised, in that they own the franchise to run services on certain areas, but subject to certain stiplulation of certain services to be retained. The operators are private companies, and are not funded by the taxpayer.
The infrastructure was privatised (see RAILTRACK), but that private company went bust, its income i believe came from selling the franchises, but the money for investment may have been subsidised. Now it is Network Rail, which is state owned, not for profit organisation, which takes its income for investment and maintenance from the Rail regulator, rather than directly from the funds from the franchises, and is probably partly subsidised by the taxpayer, on top of the incomes from the franchises.
The profits from the tickets etc are retained by the operators, but the most profitable franchises cost the most, so in theory that means some of the money is still available for re-investment.
As long as the operators and the infrastructure are under different ownership the situation will perpetuate. You could make a particluar line compleley private, so the company running the trains owns the tracks, and therefore will invest themselves into the track, but there is the risk of differing quality in different areas, plus the problem of services from other areas running on someone elses tracks. Lines could get shut down or competitors denied use, ultimately hurting the consumer.
I think the current situation is probably for the best, with private operators running on one nationally owned infrastructure. The balance of regulating the operators and managing the level of investment in the infrastructure vs the incomes from the franchises is a difficult one to get right.
