@Tarekh how are you measuring speeds? If its on a device connected by wifi it sounds like you are simply measuring the speed of the wifi connection between the hub and your device. Wifi speeds are highly variable as they are affected by the layout and type of construction of yoir home. Positioning of the hub mstters as does the level of interference. Quite why your wifi speeds are much worse with the Sky hub over your previous BT hub is unclear as technically they are much of a muchness.
If you want to test the connection between the exchange and the hub then you have to use a proven fast link to the devicecwhich would be a direct gigabit ethernet cable. If as it sounds like you are on Sky Ultrafast+ you should see spedds around 500Mb/s.
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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
