I don't like to use the repeaters because they half your bandwidth everytime you use them.
So if you are supposed to get , for example, 50m at your routers WiFi, then plugging an extender will make this half ( so 25m from where you connect to the repeater). and then so on.
But if you get an extender, then it is different as they connect to the router directly rather than the WiFi and then they broadcast the signal.
You can use the Sky one you had to get better signal. But you need a powerline adaptor to plug it into. You can then plug your sky router and give it a static IP address from your LAN range and use the broadband router IP address as the default gateway. Turn off the DHCP on your sky router. Setup the same SSID as your main SSID . and then you should be ok.