pouët.net

If I build a custom cable to connect the ZX Spectrum RGB out thing to a SCART cable does it work?

if you make it work ... :-)

No. You can't do that. Everybody else can, but you cannot.

(boring answer)

Yes, RGB-out to Scart works. You can also buy them from divide.cz (not sure why it specifically says it's for the +2 - the pinout for RGB is the same for all 128K Spectrums AFAIK) and - somewhat more expensively - from Sintech (DE shop, UK shop, CZ shop).