Firstly, is your Sky router working properly? If router does not work, make sure the router is working firstly. If yes, when you try to set up range extender, can you detect the wifi signal from your router? If range extender can't find the ssid of your router, try to change wireless channel on your router.

Thanks for the reply and sorry to take so long to get back to you.

In answer to your questions, yes the Sky router is working properly in terms of the TV and other equipment connected to it, the only thing that has the problem is the range extender.

I reset the range extender to factory settings and this then enabled my computer to see it, however although it connected, there is no internet available and I cannot connect to the configuration page via the browser. Unfortunately I don't know how to change the wireless channel on my router, would you be able to tell me how to do this?

Many thanks.

If you don't know how to change wireless channel on your router, it's better to contact your router's support to help you.
After you change the channel, try to restart the router and range extender.

Generally speaking, it will be connected if you put the correct wireless security information on the extender.
Besdies, make sure the range extender is not too far away from your main router.