Artex here too (I am an adult of the70's after all), and the fancy plaster ceiling-roses will have to go too!Be interesting to know what sort of finish you have on the ceiling. We have Artex as was standard back in 1982! So masking the fact a hole has been made was not so difficult.
But if you take the existing light down and make a connection, then shove it back up into the hole the rest of the cable can be fed elsewhere can't it?! Also a feel around when the fitting is down will prolly give you an idea of how taught the cable is and where it comes from!
Best of luck, looking forward to seeing how you did it!
I am sure it will be FUN.