@Clarex
Presumably because they are in the Sky Store rather than an inclusive broadcast channel (or Sky Cinema if you have that add-on)
In addition, some broadcast channels don't pay for on-demand rights for their content, and so Playlisting it on Glass & Stream may return a result from Sky Store.
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Sky Glass 55" (on ethernet) & two Stream Pucks (one ethernet / one WiFi)
BT Halo 3+ Ultrafast FTTP (500Mbs), BT Smart Hub 2
