It's advisable to carefully scrutinize policy offers before you purchase, since I remember a few years ago it was difficult to extend cover for treatment risk, since insurer's were of the opinion that they didn't like covering what some referred to as 'poor wormanship' (as opposed to a genuine accident which is covered by Public Liability insurance). In fact insurers I once approached insisted that the policyholder undertook accredited training and even had a minimum no. of years operating (Catch 22). Nevertheless, do check what's on offer and the limitations of cover. It may be that the first £500 of a claim is in excess.
Best regards
Pete (JS2)