Short answer – Sorry, but no you can’t.
Long answer – High Definition content is not available from the satellite Freeview service, only terrestrial. There are no plans to introduce HD to the stellite 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.
There are satellite decoders available that will upscale the SD picture from satellite Freeview to a HD picture, however this is not the same as a true HD picture as it’s only as good as the processor doing the upscaling, and t can’t introduce detail that isn’t there to begin with – you can’t make a silk purse from a sow’s ear.