Finally, I am somewhat surprised, nay disappointed, that a minority of pilots seem happy to fly in cloud without any form of radar service
Happy - no, but in some parts of the country there are times when you have no option
Also I'm going to disagree that the pilot is ultimately responsible for his own separation under a RAS.
MATS pt 1 Section 1 chapter 5 para 1.4.1
c) There is no legal requirement for a pilot flying outside controlled airspace to comply with instructions because of the advisory nature of the service. However, should a pilot choose not to comply with advisory avoiding action then he will become responsible for his own separation and any avoiding action that may subsequently prove necessary.
Now - that reads to me that until he disregards an instruction given under RAS it's the controllers responsibility to separate the aircraft - once an instruction is disregarded the pilot is effectively under RIS where it
is their responsibility to provide their own separation.