Just caught up with the latest episode.
I'm not sure why people keep saying it's 'Broadchurch style' for the killer to be someone we are not expecting. Yes Joe Miller was unexpected, but in series 2 it was the two most obvious guys who did it - fence guy and the little girls dad.
I think Katie has been raped before, although not necessarily by Aaron - i think that is why maybe she joined the police? She has already come out with several rape myths at the beginning, maybe even though it had happened to her, she really believed them (and had been blaming herself) and that's why she didn't report iyswim?
There has been a lot of rape myth busting in this series - a little ham fisted at times, but unfortunately i think it has to be made really explicit for people to get it 
I thought cath's 'of all the women at that party, why would anyone want to rape you' was brill - showing that people think that rape is all about sexual attraction when it really isn't. I think JH has been cast really well as Trish.
I think Trish might be a sex worker too.
There is no way that it will turn out that Trish is lying. No way.