@Arunprasadh are you sure the broadband speed is varying rather than thecwifi speed in yoir home? The former is very unusual the latter is pretty common. Sky test speds to your hub every day which you can see in the My Sky app service checker and yiu can see for yourself if you have a black Sky hub in its connection stats see Sky Hub statistics
WiFi speds between the hub and devices are far less certain as factors like interference come into play. Pretty typically if speeds drop at peak times in the evening and you live close to your neighbours then interference between their networks anf yours could beca factor. Nni router/hub is immune it is simoky due to the limited number of wifi channels used. Rebooting your hub can help as that causes the hub to find the least congested channel.
There are other potential causes including contention ie too many people trying to use the shared bandwidth butvthese arecrarer
=========================================================
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
