On the issue of the neighbour arrested and released on bail for assisting an offender.
I initially believed that it was unlikely that he was the person who was the "independent witness" who saw TS leave the house on Friday. There was the female witness JH whose words were quoted in the press. I therefore argued that it was more likely that JH was the witness and therefore PM must be suspected of some other crime. After all the media could, and have before been wrong. This seemed to fit with the count of assisting an offender.
Having thought some more about it, I can see how the neighbour might given a false sighting and have been arrested on that charge.
The first reports of TS were of her wearing leopard print leggings. This was later changed to plain grey trousers of some sort.
What if, the neighbour described her clothing to police based on what SH told him. Perhaps SH told PM that police wouldn't leave the house alone and that he (SH) had some Class A drugs stashed he needed to get rid of in case they were found or somesuch. SH might have told PM what TS was wearing when she supposedly left the house on Friday and PM repeated that in a statement to the police. The matching clothing description means this is a "confirmed" sighting.
On Friday 10th, CS leaves the house (not under arrest), a body is found at around 17:00 and SH is later arrested at around 20:00. We learn from the papers the next day that CS and PM were arrested late on the Friday evening.
If you read the CPS definition of Arrested on Suspicion of murder it says that
The offence of assisting an offender ("the principal offender") is committed when:
the principal offender has committed an arrestable offence;
the accused knows or believes that the principal offender has committed that or some other arrestable offence;
the accused does any act with intent to impede the apprehension or prosecution of the principal offender; and
the act is done without lawful authority or reasonable excuse.
It goes on to state one such example as
lying to the police to protect principal offenders from investigation and prosecution
Isn't possession of Class A drugs an arrestable offence? Yes it is
In this scenario, would PM have lied to the police to protect the main offender of a charge of murder,
or some other arrestable offence? Yes he would.
It's always easier to downgrade a charge that upgrade it. And let's not forget that, at this point in time, PM has not been charged.
My point is that PM would not necessarily have had to know that SH's crime was murder.