It is the former ('twisted' stuff from Woolworths etc.) that I recall being used, and was talking about (most commonly transparent/ translucent/ colourless) - and I'm sure that I still have plenty lying around somewhere!Ah but let's remember that different peoples idea of bell wire vary. To me it was the variously coloured thin twisted stuff from woolworths, to some it is the twin solid wide spaced (To fix with a pin through the web), or twin solid fig 8 about 1mm².
Personally I've never classed the figure of eight twin flex (in OP) as bell wire, but I'm sure others do, and it was certainly sold as mains flex in yesteryear.
Kind Regards, John.