All in all, I would say the UK privatisation program was successful. It's not perfect, and I think it's the governments fault in not structuring and regulating sectors/ utilities as best it could. The private sector will do what it will, within the law.
Take the Banking and financial sector, what a massive mess we made out of regulating it. If you want an example of how a privatised sector has worked really well you only need look at Telecoms as a successful example.
Also privatisation became a global trend in recent times, following our lead. Article is here: http://www.independent.co.uk/voices/comment/thatchers-economic-reforms-influenced-the-world-but-the-next-big-changes-wont-come-from-britain-8566165.html
What I don't really understand is the scepticism, we see it work well with other products and services, (room for improvements in some cases, sure) so why not across the board. What are people so distrustful about? I'd be much more inclined to distrust politicians and government departments and bureaucracy to manage industry and services efficiently.
When it comes to wasteful spending, no one really has a patch on them.