@P4rls measuring speeds on a device connected by WiFi records the slowest part of the transfer. Sky guarantee a minimum connection speed to your hub. No isp will guarantee that every device connected by WiFi will get that speed as the layout and type of construction of your home affects the WiFi signals through in the inevitable interference from other networks are outside their control.
Where you have Sky Q boxes acting as wifi hotspots the data will often have multiple WiFi jumps and bandwidth will be reduced when the tv box is in use. You can improve WiFi speeds provided by a Sky Q box by improving its backhaul connection to the hub when I had Sky Q one of my Q minis provided slow wifi and could sometimes lose the Tv signal so I used a set of powerline adapters which used the mains wiring to carry data between my hub and the remote Q box I found this cured my issue.
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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
