Sky is one of the few on-demand services that actively and deliberately block Airplay. So, as mentioned above, there is no way to do this.
Almost everyone has a different explanation why Sky do this, but whatever their reason, it is quite sad and disappointing from them, and one of the main reason I have no interest in subscribing with Sky.
One way you may be able to do this, is by using a Laptop connected to the other TV?
Alternatively, something like the Favi Smart Stick may work (though I am not absolutely sure)