@Gosia75 the age of your Sky hub should not be an issue as long as it isnt the type on the second line in the picture on this page https://www.openreach.com/fibre-checker
You do need a relatively strong Wifi signal to stream video however decent bandwidth is only half the story as stability is just as important. First thing to check is the position of the hub which should be in the open on a surface so its above obstructions like radiators. It is worth rebooting th hub by removing the power for a few seconds as that will cause it to find the least congested wifi channel.
Newer hubs while having new functions do not have much greater range - the power they can use is limited by regulation. In many homes you need more than the free router any isp can provide. There are loads of third party solutions and Sky sell add-on packages like Wifi Max which can have up to 3 extenders.
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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
