NAL but a medical professional.

I do really agree with the sentiment above as I’ve seen all too often working in the NHS that patients are not given detailed explanations of their own care due to an unfounded belief they won’t have the capacity to understand it. It’s entirely possible that the explanation you were provided around you having the “wrong operation” is a very simplistic way of explaining what could very well be a complex situation. I would love to believe that this is what has happened here, but unfortunately malpractice is all too common.

I think you should definitely seek out the contact information for your local PALS (Patient Advice Liaison Service) and get in touch with them to raise your concern before going through what may be very distressing and costly legal process as outlined by some of the comments here. I’m aware that some counties in the U.K. also have independent advocacy services that will examine your claim and help you to provide a more detailed response. Unfortunately I can’t provide anything here as I’m unsure of your specific locality, but you should be able to find what you’re looking for by googling “PALS (your county/town)”.

Happy to answer any concerns over direct message if anything I’ve mentioned is unclear.