I am a surgical trainee so can't answer from personal experience. This post is in a forum for medical school applicants so I don't know how many psychiatry trainees will be floating around.
My impression is that there is a recruitment crisis in psychiatry with most regions unable to fill all of their posts, even at a junior level. See
http://www.rcpsych.ac.uk/pdf/CT1%20fill%20rate-10.09.2012.pdf I suspect this is good news for you as there is more likely to be an open attitude towards people coming from overseas.
After FY2, you apply for core training in psychiatry (CT1-CT3). I am told by a colleague that this means rotations through child/adolescent, old age, hospital liaison, substance abuse, etc psychiatry. I am also told that specialty registrar training begins at ST4. Unlike other hospital specialties, you enter ST4 to learn a psychiatric sub-specialty, e.g. you have to decide at the beginning you want to be an old age psychiatrist. You then spend the rest of your training (until ready for consultant posts) just doing that sub-specialty and qualify as an old age psychiatrist only.
Mental health in this country is notoriously under-resourced and I suspect the recruitment crisis just makes life harder for everyone else in the specialty. Someone has to cover all of those gaps in the on call rota, do extra clinics, etc.
Working hours are generally better than in acute hospital specialties. A lot of on call work is done by mental health nurses supported by doctors when necessary.
Doctors in the UK are paid the same regardless of specialty (a consultant psychiatrist is paid the same as a consultant cardiothoracic surgeon) and you can find national pay scales easily through Google. There is plenty of scope in psychiatry (particularly some sub-specialties) for private practice and medico-legal work (writing reports, expert witness, etc).
Research isn't a necessary component unless you take a combined clinical/academic post (the Academic Clinical Fellowships) but I suppose your exposure to research will depend on where you train. In general, if there is a Professor of Psychiatry at the nearby medical school then there will be a research programme. MDs/PhDs are not mandatory for progression as they are becoming in some other specialties.
I don't know where the MRCPsych comes in - this is another one for Google.