Mine specifically says
"9 Care of equipment
We own the equipment at alltimes and you must not:
(a) remove the equipment from the home without our prior written conset.
(b) sell, lease, dispose of lend or otherwise part with posession of, or modify in any way, the equipment"
The equipment is defined as the Decoder, Smart Card and Antenna system.
I understand from this that you cannot include it in a sale and puchase agreement as chattels and in fact you can't even change the LNB yourself as that is effectively a modification.
And section (c) indicates it can be used only for the Sky service and no other programming which means you can't even legally connect a Freeview decoder to the dish and use it.
Pays to read the fine print when you sign a contract particularly when it's all in favour of Sky and leaves you with virtually no rights as the subscriber.