Help - who did kill all the women?

It's a great show, especially season 2, but I am a bit confused.. Did we get to know who the killer of all these women, was in season 2?

We know who killed Vicky Flemming, but who killed Tommy Lee Royce's mother and the other women?

If it's not just me, who do you think killed the women?

I have 3 suspects:
1) Daniel Cawood (Catherine's son)
2) Clare's boyfriend (Catherine's sister's boyfriend)
3) Nevison (The father of the policewoman Tommy kidnapped and raped)

Nevison is the weakest suspect, why would he kill these prostitutes? I picked him, because of season one, and the death of Ashley Cowgill, the guy who organized the kidnapping. Nevison's motive should be revenge. But it's probably not him.

Clare's boyfriend, also a weak suspect, though I did put him there, and did so becuase of his behaviour, there is a bit Dr. Jekyll & Mr. Hyde about him..

Daniel Cawood, well he is my strongest suspect, but he is not a 100%'er..
I made another post about him.

But there is clearly something strange about him too.. I mean what was that about his wife, who suddenly kicked him out, and he haven't told us why, other than he said, she gets these weird ideas?
Also I think there was more to Becky's death, and maybe..

What do you think?