It looks like you're getting it in the neck, today, Messy!
I'm with you on mentioning relevant new eBay listings: as Jim says, that's what you're asked to do, and surely, when many thousands already know of a listing direct from eBay, it makes sense for all the few here to know of it too. It's not the job of those who read this forum to protect a few individuals from (very slight) further competition, but it is their job to discuss what's happening - or appearing - in the world of unusual microcars.
As to the mass listing of parts you want to sell, though, I feel that's not appropriate here. You regard it as not commercial, but how can it be not? If you're giving the stuff away, then it's not commercial; if you're selling the odd car or part which was yours in use, then it's not commercial. If you're making, or having made, or buying in, a wide range of parts with the aim of selling them, though, then that's commerce. It might not be "your main job", but it's commerce, and whatever way the forum treats your commercial activity has to be the same way it treats the commercial activities of, say, Halfords - otherwise it would be unfair on Halfords!
The simplest way forward is perhaps to start a website, and show on the forum a link to it. (Or photograph the list, and stick the pic on any of the free picture services?)