Hi F_D, went into Cerilog once again in CT to get some RG-6 though they only can supply 50-ohm cable by the bulk.
The chap was very helpful about the whole thing and was willing to get some from Joburg if necessary.
He also mentioned that I could try Regal Security as they do extensive CCTV installations and are in the same Business Park, so that's what I did.
Again the Regal chap was unable to assist as not being a trade dealer, though advised Bright's Hardware, where I found Ellies 'DSTV Approved' RG-6 @ R4.80 per metre promptly buying 20m, and pulled it through my lounge conduit and ceiling on the week-end.
Now for an extra question: does the FM dipole ideally be need to be mounted outside, or would indoors ie. oriented vertically inside on the roof rafters do?