BMI hospitals - poor consultant

not so long ago I wrote a thread on a consultants terrible attitude

I got some very good responses,

I also got an apology from the chief exec at the private hospital(s). This is a large well known UK private medical hospital company

I am pleased from the apology I got from the chief exec, and I was told a thorough investigation would take place

now after many days beyond their own promised date of delivering this investigation, all I get is a single page A4 reply from the local director at the hospital in question saying that because the consultant is self employed whilst providing consultancy services at their premises they are washing their hands of the matter

basically the consultant in question failed to diagnose a worsening health condition (potentially life threatening). Although my own GP had written to him explaining what was wrong with me ( and he turned out to be correct), the consultant chose to ignore this letter from my GP

has anyone else had similar situation where you went to see private consultant at private hospital, received poor service, and you complained

what other authorities did you use, go to, to get advice, take action
?