I assume you want to get ntl digital channels on the upstairs TV ? If so, then you would be limited to the digital channel selected downstairs, i.e. you wouldn't be able to change digital channels from upstairs, not would you be able to watch, say, BBC3, upstairs while a different digital channel was being watched downstairs.
Besides that, it is possible, though you would need to buy something like a VCR and get a lot of coaxial cable laid.
In summary.
- SCART OUT from ntl digital box to SCART IN on VCR,
- Coax (RF) OUT on VCR to coax cable running from downstairs to upstairs TV
My advice ? Pay the money to get a second ntl box upstairs. Way less hassle in long-run.
Also, FWIW, IMHO TV in the bedroom is a no-no.