The problems that people seem to have with Osteopathy, Chiropractic and even physiotherapy to an extent, are largely based in the professional historic foundations. A bit like allopathic medicine historically had some very odd beliefs and philosophies - think the four humours and bleeding, so too did osteopathy and chiropractic. However those beliefs are historical and, just like with allopathic medicine, chiropractic and osteopathy has moved on. There is still a long way to go before every mechanism is understood, there is a problem with funding large scale trials and there is also a problem with a minority who still believe the old philosophies and that they really can heal the world. However the vast majority consider themselves to be specialists in their field, evidence led, patient centred practitioners who learn from experience and are trying to move their professions forward by contributing to research.
The difference between the professions is, IMO, largely historical. Any good practitioner will look at what others in their field are doing, question its effectiveness and include it if it suits them and their patients. Private physios are as much primary health care professionals as any osteo or chiro and is just as qualified to do any of the techniques.
At your initial consultation with a manual therapist (Physio, Osteo or Chiro - stick with these as they are protected titles and really have studied for years to gain the title) You will give a full case history including medical history, you will be physically examined, you may be sent for further investigations including X rays, MRi or even bloods, following all of this you will be given a report of findings including diagnosis of your condition, suitability for manual therapy (If needs be you will be referred to someone more suitable for you), personal, individual plan of management including risks, you should also be made aware of your prognosis, all before treatment even commences.
Treatment is always patient centred as you personally have a completely different history and physiology to your neighbour - so what suits them may not be appropriate for you.