@Ellarose007 if your phones are switching to use mobile data check their settings as iPhones and some Android phones have a setting which does this if mobile signal is faster which can be the case if yiu have goid 5g reception. On iPhones its called WIFi assist and is at the bottom of ghe mobile settings.
However if you find you TV's cannot stream you may simply need additional WiFi kit as in many homes a single hub is not sufficent to give coverage in every room. Sky will sell you their WiFi Max bundle thst can provide up to 3 extenders see https://www.sky.com/help/articles/sky-wifi-max or you can use your own WiFi kit if you prefer.
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65inch Sky Glass, 3 Sky Streaming Pucks, Sky Ultrafast + and Sky SR213(white Wifi Max hub) main Wifi from 3 TP-Link Deco M4 units in access point mode
