Very interesting information TotalBeginner. If you wish to take action, then it is off to your local Trading Standards Office (part of the local Council) to start the ball rolling. The problems of doing that, you will already know.
You will have to spend time and money and, if you use FR regularly for your leisure travel, face the risk that they will decline to carry you (as they are entitled to do and not tell you why). But, crucially, you have to be able to prove that they overbook. That would mean providing documentary evidence.
There are other avenues available to you but only the legal one will have any effect. Don't tell the media to gain publicity as that will almost certainly be challenged by the company and they might try and take you to court. FR will be betting that the effort and money are more than you are prepared to give. Again, thanks for letting us know.