Short answer – Sorry, but no you can’t.
Long answer – High Definition content is not available from the Satellite service, only Terrestrial. There are no plans to introduce HD to the Satellite service. If you aren’t in an area where you can receive Freeview HD from a terrestrial transmitter, the only option to get HD at present is Sky’s MySky HDi system, through which TV3 and a few movie and sport channels are in High Definition.