The Competition Commission are investigating the practices of private medical insurers (PMI's) and there have been angry protests by patients and doctors (read here) .
Patients should ensure that they are really fully covered for all aspects of their surgery and follow up appointments. It is very common to find that an aspect of surgery (such as a multifocal lens) or the number of follow up visits may be limited and that patients may in fact need to top up themselves. This seems very common where people are given health insurance as part of their occupation and then find that in fact they have very basic health insurance with a number of limitations. To avoid further stress at a time when you may already be concerned about your health you should speak to your insurer about the depth of your actual cover.