I don't believe Joanna got home either-----but where does Father George Henwood fit in? I was always under the impression that she was very close to home when she met him, much closer to home than the Hophouse pub---which is , I think , a good 7-10 minutes walk from her flat.
We don't know that the person Fr Henwood saw was, in fact, Joanna, of course. He assumed it was, but he did not know her.
Interesting re the mobile phone. IMO, Joanna would have taken her phone out of her coat pocket, as she was awaiting replies to her texts---or, at least, one reply. Why text people to see if they are free, and then not bother looking for the reply?
It seems, to me, unlikely that Joanna would have been killed within minutes of arriving home---unless someone was already in her flat. There was, apparently, no sign of a break in, so who had keys, apart from Greg and CJ? Really doesn't seem very likely.
IF someone was being "set up", that person could have been Greg, but it could equally have been anyone from the house----IMO, of course.