Hi
are you sure it is a screw-on connector?
It's just I'm fairly sure NTL use crimped ones, but I don't know if that is the case with Telewest?
Is it not possible to drill the hole large enough to pass the connector through & 'make good' afterwards?
- but to answer your actual question, no, the house electric doesnt need to be switched off, just whatever modem/stb the cable connects to.
