Where everything is falling down for me the most is how the accused is supposed to have taken Alesha from the house.
This is a property that he had never been inside other than perhaps buying drugs from the door (which can be used to explain away the handprint in the stairs leading to the flat) according to RM, but he would've had to get inside it, somehow locate Alesha's room despite not knowing which room it is, take her from it despite the family (I think TM, actually) saying that she would scream if someone she didn't know came in her room, then exit the flat all without waking anybody up or leaving a single fingerprint.
It is possible but is it likely given how clumsy he seems to have been disposing of clothes, the knife, running in and out of his house several times, etc?