I sent a letter to ITV reference Dolby Digital 5.1 surround sound and here's the reply.
Thank you for your email regarding HIGH DEFINITION.
Unfortunately ITV HD viewers do not have access to Dolby Digital 5.1 audio at the moment. However, ITV hope to be able to offer it ‘later this year’.
May I take this opportunity to thank you for taking the time to contact us here at ITV.
Regards
ITV VIEWER SERVICES - PR
So its "Coming Soon" so I had to post it here