These are not your everyday Astra car being knocked out for a couple of grand which suits a huge population of families - it will take some time for the right buyer, to come along, be local, like the colour, the version etc and come look. I have seen pristine cars sit on here for months without selling (could be time of year also having an effect).
ebay has always been my place of choice to sell a car - biggest audience, best flexibility for writing an ad, including videos etc. Autotrader I find doesn't attract the right buyer group.