As Nerol says in the UK practitioner psychologists are trained at doctoral level, and the equivalent of this would be required to register with the HCPC. More than that is that we are supposed to demonstrate specific competencies in applied settings, which UK doctoral practitioner courses are required to cover and assess. You would have to demonstrate you have achieved a comparable level of academic, research and clinical work, which would be difficult with the background you have outlined. You will have to talk to the HCPC and go through with them to see what is missing and what further training is necessary.