I think PIREPS are not allowed due to possibility of misleading information. In the past I have seen the runway from a few miles off, but getting closer entered a fog bank and it disappears.
Some people above are suggesting that recognition of a fact and learning of a fact are different things - yes that is true, but good training will help you recognise what you know to be the facts.
Also people are saying that STN is really busy and so things may have been missed and that humans make mistakes. Well these things are true - we do make mistakes and STN is busy. However, STN is no so busy that you forget to do your job (I fly into or out of somewhere busier every day). And we are not talking about one or two mistakes being made - we are talking about a large number of aircraft landing below limits, so therefore a large number of mistakes. If indeed a lot of aircraft did land below limits, then it proves that Ryanairs training/awareness/culture leads people into making these mistakes and so therefore needs changing. QED.
If the reported facts are wrong and aircraft didn't land below limits, then that is a different matter.