Surely the police would know if Twine Boy lived in the cottage overlooking the lake at Axehampton? They have interviewed him; wouldn't they have to ask his name and address as part of the interview?
I was thinking about the significance of the dates; they are in or close to half term. The police don't seem to be following that line of enquiry, however. The May dates have Kath's birthday in common, and she was away on the dates in question (or has changed her calendar to make it look that way). Kath believes Jim to be the rapist, or wants it to be Jim, or perhaps wants to punish him for cheating on her.
Taxi Man seems to me to be the most likely rapist; he is contemptuous of women and certainly has the opportunity. Then there's the trophy drawer, although that could be stuff his passengers have left in his cab.
He could have acted alone, shining a phone light into Trish's face to prevent her identifying him.
As a pp said, Trish's ex's secret was the spyware and Ed's secret the stalker pictures. Have I missed someone?
I think that Mark surviving being pulled out of the water is intended to be the beginning of closure and moving on for him, thus bringing Danny's story to an end.
Like others, I do hope the rapist won't turn out to be one of the peripheral characters.