Hi Jon. I've been running my physio clinic in New Zealand for over 5 years so unfortunately cannot give you the percentage patient-type split since I'm not in the UK.
However in terms of buying a private practice - yes, you generally buy the existing clientele as well as physical assets (equipment, etc). This is very important as your patient or client list takes time to build so if you can buy it - it is certainly a bit of a shortcut to success. You can market to that list virtually for free to get returning clients buying more of your services/product. Do you see how valuable it is. Much better than paying for expensive advertising to attract NEW clients/patients.Always insist on 'taking over the prctice's patients' when buying one... otherwise what are you actually buying?
Another advice I would give you is get some business/marketing training. Most of us physios... well, lack business skills and hence make lots of mistakes and struggle to earn a good living. I have a business coach who I have dealt with over the years and it certainly helped me immensely (he is reasonably priced too). Let me know if you want me to share his contact details.