Everything keeps disconnecting from my wifi

[#1]

Hi, since switching to plusnet, my iPhone , laptop and my partners laptop often disconnect from the wifi. 
Quite often my laptop disconnects on the Wi-Fi and also when I try to connect it says it cannot connect to this network, or it can connect to the network but tells me there is no signal. This is very frustrating when it happened several times a day and I need to be on my laptop for work from home. My iPhone keeps coming off the Wi-Fi and going onto 4G continuously lately , which is very annoying when I’m trying to use my iPhone to stream onto a chrome cast. Can you let me know why this is happening?

[#2]

Use search box here to look for WIFI issues (+ solutions).
If you have a dual band router, make sure both channels are given SEPARATE SSID's, as a starter.
Use a wifi analyser app to check frequencies most in use around your home, and then manually select LEAST BUSY, and enter into your router, rather than using AUTO.