Jessi - this bit doesn't read right. Who is the "Isle of Man head of investigations police"?
To get any traction you need to report this formally and make a criminal complaint https://www.iompolice.im/report-it/sexual-assault/
There's no time limit here and the website says you'll be spoken to by specially trained officers. If you ring, make notes of your call and the name of the person you spoke to. These things should be treated as serious from the outset. Your abusers need to be dealt with.
Holding social services to account - especially if no crime has been committed - is going to be difficult. Your best bet is to speak to an advocate who should be able to outline your options.