falseprophet - as I said in the very first words of the post you quote from, "keep in mind the crime he was found guilty of".
If you have information which can protect others in the future, which would lead to a stronger sentence for a convicted sex offender, then it's on you to report that to the police.
If this is ongoing abuse, then you can contact the NSPCC too. 0808 800 5000 is their number. They can also advise you on the proper course of action even if it is just suspicion.
The safety of children and teens has to be the priority over whatever dispute you have with Simon, surely?