Back in the 1990s the Maudsley sent a CPN out to assess the situation if they were called about a crisis and if necessary took you in. Don't know how widespread this was - but the Maudsley did this.
Throwing the onus on the person in trouble is surely part of the problem. I don't know what happens if you turns up at Kings saying you are depressed/suicidal/voices etc. If they treat you like someone with a cut finger you might have to wait, or be told to ring your GP in the morning.
This link comments on the scheduled closure:
Maudsley psychiatric emergency clinic to close - Community Care
There is an options paper from 2005 written by or for Patrick Gillespie who was SLAM's Chief exec at the time. This claims it was not a money saving measure, rather a re-configuration of service (Libraries?)
It was hotly contested at the time by many users, MIND groups and other user groups and at least one councillor I think was chair of Scrutiny at the time.
http://moderngov.southwark.gov.uk/Data/Statutory Joint Southwark Lambeth Health Scrutiny Committee/20060221/Agenda/Appendix A SLAM formalconsultation document, November 2005.pdf
response to scrutiny here:
http://moderngov.southwark.gov.uk/Data/Statutory Joint Southwark Lambeth Health Scrutiny Committee/20060420/Agenda/SLaM covering letter tojoint committee Chair Councillor Angie Meader.pdf
Not being a SLAM staff member or archivist I have not been able to see any description of the service as such. I guess it might be in their annual reports prior to 2006?