Originally Posted by Funkstar 
DVB-T doesn't work like that.
Easy way to test this. record a program from every isntance of C4 on your system. Them open them up in something like VNC or MediaPlayerClassic and check out the stream properties. I'm guessing they will not be HD resolution. In fact if they are normal TV resolution, then C4 have changed their broadcast stream as they use to be sent out as 640x480 or something similar to reduce bandwidth.
4 on Freeview is broadcast in 704*576, at between 0.7 and 1.6 Mbit