As regions are gradually switched to digital you will need occasionally to retune your box - do it through set up or whatever applies to your box. You may need to do this several times during the switchover period even if your area has not yet changed over entirely.
I,m on the Winter Hill Transmitter the same as yourself and my Freeview has been OK apart from some signal Break-up due to the weather. Our switchover date is Nov 4th until Dec 2nd.
Try a Full Re-Scan if you have no Channels at all and see what happens. Are all Channels 'Off' or are some still 'On' ??