Lets try and rule out the ntl box. If you unplug the STB from the wall, and disconnect all cables between the STB and / or VCR and TVs, can you get a signal to the TV from the VCR? i.e the only cables that exist are power to TV and VCR, and an aerial from VCR to TV. At that point if you cannot tune your TV to the VCR, then it
has to be something odd with the VCR.
I am of course assuming that you have your STB connected to the VCR and TV by a coaxial aerial type lead. Or are you using any scart leads?