@AnnieF3 ifyou live in a 2 bed flat then almost inevitably you will have serious wifi interference issues..Given only 3 or at most 4 networks can co-exist on the 2.4GHz wifi band without interference and you are likely to be within range of many more than that it is pretty certain. Install a wifi anayzer app on your phone and you will see what I mean.
If you buy a 500Mb/s full fibre service the full 500Mb/s will be accessible over an ethernet connection. The Sky hub should give you access to the full speed over wifi in the room the hub is placed assuming it is out in the open on a surface so its wifi signal isnt being blocked by furniture etc. However move a couple of rooms away and spedds will drop and you become clooser to one ofyour neihbour's router which will interfere with your signal if it is using the same or adajacent wifi channel.
There are things you can do modern wifi mesh systems can use a wider range of wifi frequencies and can use AI to minimise inteference. Sky's own WiFi Max bundle uses WiFi 6 which helps quite a bit so it maybe worth upgrading to that if you want a simple solution but you can do better with a third party kit.
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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
