I have been through this process, acting as representative for a rescue.
Firstly I arranged a formal meeting with the Clinical Director of the practice in order to discuss the issues. I was not satisfied with the outcome of the meeting and his proposals to ensure that this would not happen again.
On behalf of the rescue, I then took the matter forward as a formal complaint to the RCVS. This was a serious issue involving two rabbits and what should have been routine castrations. The RCVS investigated, but did not rule in our favour. I considered that we had a watertight case, we had graphic photos at various stages of the process, medical reports from my vet (who had to put right the infected mess made by the rescue's vet), medical notes from the original vet, a number of witnesses, but it was not enough.
The RCVS complaints form asks what outcome you would like to see....our request was only that the vet responsible should be made to undertake additional training and update her knowledge with regard to rabbits, in order to make sure this did not happen again. The RCVS made no recommendations and she was free to continue practicing and operating with her current level of sub-standard knowledge and expertise.
I was, and still am, very disappointed in the outcome and it left me with little faith in the RCVS. I am glad we went through the process as at least we tried.