At the moment you can get Channel 4, BBC and BBC 1, STV, NHK World and ITV 1 transmitting in high definition but Channel 5 have signalled their intent to transmit free to air HD programming. I hope this will happen sometime during 2012.
BBC sports broadcasts look good in HD and they are transmitting more films on their HD channels although their low bitrate causes some image issues. Hopefully the BBC will listen to customer complaints and up their bitrate, really we need around 16 to 18mbp/s for really good quality. I actually sent a complaint to the BBC recently asking that they raise their bitrate back to previous levels and that they start transmitting all their films in HD.