He didn't actually confess to killing the girls. just that he'd done some bad "things". In fact when his mother asked if it was to do with the girls he said "Why would you say that?"
After she mentioned the damage to the red vehicle, she asked why he had woke her and then realised it was bad news and asked was he responsible for the death of those women. He said yes.
Ive give up tv speakers and switched to high quality headphones and I can hear every word of the script and the high quality music, especially on Happy Valley.
^^^ I worked for years in 'Happy Valley' and lived there for several years, so the accents are not a problem and I recognise a lot of the settings - even so, I was confused tonight.