coax is a single cable (like the one you probably used to use to connect to an aerial). your tv may well not have an input for this!
the red/white/yellow are known as RCA
i guess you've got 2 options:
TV <---scart---> VCR <---scart---> NTL
|
\--rca---> DVD
VCR <---scart---> NTL
|
+-- splitter thingy ---> TV
|
DVD
ah the joys of ascii 