got this email from Humax : ( hope its of help to forum freesat/view:ers )
Dear Humax user,
Channel 4 have scheduled a change to the transponder that carries C4 HD.
The change will occur overnight on 27th March into early hours of 28th March – (23.00 to 03.00), and we therefore expect that C4 HD will be unavailable for a maximum of 4 hours at this time.
Humax freesat products will rescan for channels if left in Standby mode so the changes will be detected, however in the unlikely event that your product doesn't find this change or is powered off overnight a “freesat Tune” will be all that is required to fix this issue.