@David-TP definitive proof that the Deco BE65 after the latest firmware update is the issue for me. I have connected the supplied ISP router and the high latency has completely disappeared. I had another disconnection 7:30pm tonight and since the supplied router nobody in our house is complaining about lagging/latency. I will post more screenshots after the Easter weekend with the ISP router connected. But so far our connection is more stable now. 

So with the suppiled router been online since just after 7:30pm last night. My oldest son was gaming throuthout the night and has said the connection is more stable 100%. Apart from my oldest son we were all out yesterday until after 3pm. Once we were all online until the random disconnection just before 7:30pm, the connection is very unstable. Now with the supplied ISP router in place. As you can see it's now back to normal. I did notice last night the Deco app for IOS had an update version 3.9.50 "Fixed some bugs and improved the stability" I assume that's for the IOS app only. But until I speak to an TP Link engineer via remote session, I will keep the supplied router connected.