@will657 talk to whover manages the building as they will probably becable to tell you how the built-in system works often they have a single contracted supplier who provides the connectivity and pays the freeholder a fee. As @TimmyBGood explained Sky only use Openreach's network.
When you say you have an issue is that with wifi in the flat or thecspeed delivered over ethernet? You can use a third party router if you want Asus make a range many customers have connected to Sky FTTP services. These can often provide bettercwifi speeds but are still subject tomthe laws of physics.
However before spending money consider the following, inteference between neighbouring networks is a common issue especially in flats where you can have 10 or more networks within range. Install a wifi analyzer app on to a ohone or laptop and you will see the signals with the strength and channel. Two signals on the same or adjacent channels will interfere the stronger the second signal the greater the effect. There are are only a limited number of channels. This esecially affects activities like gaming or streaming video which is why use of ethernet is advised.
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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
