Have you updated to the the latest version of software? There was an update 115 which added Channel 4HD.
The current version of software is now 116R. You can manually update your receiver within the settings menu - both over IP or via the Satellite.
Hope this helps and let me know how you get on.
Sorry for the delay but the sudden loss turned out to be due to very high winds having moved the source sat aerial. I have only got back and have not as yet had the dish re-aligned but assume this will cure my problem.
Thanks a lot for the interest shown and apologies for not setting the matter sooner. As you may have concluded I am new at this forum business.