Any TalkTalk service that is non-LLU which this looks to be suffers worse contention, so you would probably get better by changing provider even if WBC was not on the way.
When you say connection speeds are better in the morning, do you really mean the 5952000 figure, or the result from a speedtest. if the 5952000 figure is varying a lot then you probably have a wiring issue, and if the 23dB attenuation figure is the downstream attenuation I am tempted to say you do have a noise problem.
In short the full set of figures (screenshot is better to avoid missing useful snippets) when connected to your master sockets test socket.