Manic
The Times, Telegraph, Independent and Guardian are the serious newspapers in the UK and cover the full range of editorial from across the political spectrum between them. The Mail is a tabloid celebrity gossip scandal rag. Just look on the sidebar of the link you posted.
http://www.youtube.com/watch?v=5eBT6OSr1TI
There was a move to use the word client in the UK a few years ago but this was in the context of a socialised service where one of the problems was that people often received a rather brusque and impersonal service, especially in hospital. Its use was meant to address a poor service culture rather than be precise about peoples relationships directly. The poor service culture was a big problem so that was the priority. The use of the word client was intended to help address the fact that people were being treated badly.
The service culture in the NHS has been addressed to some extent but certainly the problematic use of client and consumer is well understood especially in the context of a socialized service that historically has not focused on people choosing one service or another. I have not heard or seen client in print for a long time.
Service user is the most common generic term and patient is not forbidden, it just is used less and less.
The use of patient/service user is typical as in the General Medical Council link below.
http://www.gmc-uk.org/about/valuing_diversity_effective_communication.asp
From the Royal College of Psychiatrists. The quotation below is a typical example of the way the use of people and service user have become ubiquitous.
http://www.rcpsych.ac.uk/campaigns/fairdeal/whatisfairdeal.aspx
e.g. Engagement with service users and carers must be meaningful not tokenistic. People with direct experience of mental health problems or a learning disability should have a central role in the design and deliver of mental health service.
Kugel
No prizes for guessing. 1.2 million staff. $250 billion budget, serves a population of aprox 60 million in an area roughly the size of Texas. It is a highly socializing bureaucracy, so while their will be some diversity the generic term service user will be fairly universal in adult mental health.
In this sticky thread essential articles
http://forums.studentdoctor.net/showthread.php?t=289443 post #32 by erg has an article attached The death of phenomenology that charts the decoupling of American and Anglo Europsychiatry up to the 70s before the publication of the DSM 111. I am not saying this is happening again in one way or another but it certainly may. The article posits a midadlantic movement that included John Hopkins (I think), any way the suggestion is that there is a huge diversity in North American Psychiatry and I expect that is probably true. Of course I dont know.