@Joseph-TP 

Hi, thanks for the information in your reply. I have now tried the resets you suggested a few times but there is still no WiFi network visible. 
I have 3 solid led's on the Adapter. The extender has 3 solid led's as well. 
With all the resets I have tried there is no WiFi network visible on my iPad only the main router and my printer. 
Sorry but I suspect there is a fault with the units. 

  @Alir 

Hi,

Of the 3 solid led's on the extender, can you confirm that one of them is the Wi-Fi LED   ?

  @woozle 

Hi, yes it is the WiFi led that is on. I don't have an Ethernet cable plugged in to it. My Ethernet cable is on the adapter. 
 

  @Alir I chatted with an online agent tonight. After a few times resetting to factory settings I am now able to connect to both channels. 
I still have to work out how to make the system apear as one network and not have to join the new channels instead of the main router. 
maybe this is not possible with a talktalk router. 

  @Alir 

Wi-Fi Clone should also be possible with a TalkTalk router.

But even if it doesn't, then just change the network names and passwords of the TL-WPA7617 manually to match those of the TalkTalk router. Make sure you do it for both frequencies, 2.4GHz and 5GHz.