In this day and age, the very first place anyone looking for a classic car goes is ebay. I would be willing to put money on that. Do a lot of classic cars get sold on ebay, no...but they get seen on ebay leading to a sale one way or the other.
I don't pay attention to Sprites or 6 cylinder cars, but I do watch 100-4's pretty closely. Do yourself a favor, go to ebay motors, go to cars for sale and list austin healeys. Then click "completed listings" (you will need an ebay login to do that) and sort by "year -oldest first". Start from the top and click on the 100-4's, there are currently 8 cars, half of which were listed on, then sold off ebay (two were sold for asking price on ebay and the remaining two have "dope smoking" prices, hence they will never sell anywhere).
My very recent personal experiences: I sold a Jaguar a few months ago, listed on this forum, the Jag forum, autotrader and ebay. No action anywhere except ebay where someone saw it, then we worked out a deal locally. Two weeks ago I purchased an '87 911 Carrera, initially saw it on ebay at a relatively local dealership, then I went there and worked out a deal.
In shopping for that car I religiously checked ebay <span style="font-weight: bold">every</span> morning, followed by a Porsche forum and only looked at autotrader classic once a week and Hemmings maybe once a month (in desperation). Don't get me wrong, I like Hemmings, I found my Dad's old 100-4 there which I now own...but that was in 1994, things change.
Sorry for the length of this post,
Wally