So, if I have this correct...
NM is claiming that he put Becky's body in the boot of the car on Thursday Feb 19. He and SH then stay at Becky's home all day and only return to CML about 7pm, have a takeaway and watch tv.
On Friday Feb 20, they go back to Becky's house during the day and are there when the police call round, after Becky has been reported missing.
All this time Becky's body is still in the boot of the Zafira which is presumably parked just outside the house !
Then on Friday night, NM and SH go back home to CML, NM waits til SH is asleep and then goes out to the car, brings in the body and puts it into the bath and locks the bathroom door.
On Saturday Feb 21, when SH gets up , she is not able or allowed to go inside the bathroom.
NM then takes SH back to Crown Hill, Becky's house, for the day ( minus the shopping trip together obviously ).
While SH stays there ( hopefully this will be corroborated by DG and AG ) NM nips back home, gets out the saw and does the dismemberment.
By the time he goes back to collect SH and bring her back to CML, he has already hidden the pieces of the body in the house - that bit I can almost believe, so much cr*p in there, no problem hiding stuff - meaning the bathroom is once again available to use.
Not that I believe much of this, just wanting to get Mr Metro/Neanderthal's story straight in my mind.