I suspect the market is wising up to the somewhat flaky provenence of these so called "continuation" cars from AC, hence the failure of COX3361 to reach its reserve. I also think that many of these cars are tainted by the Lubinsky connection.
While the genuine cars are increasing in value at a depressing (at least for those of us who don't have one) rate, anything without real history and provenence is viewed with suspicion, which is reflected in the value.
I've read many claims about the quality of the later AC built cars, but in my experience, which admittedly, isn't vast, the quality isn't that high. You certainly wouldn't want a polished aluminium body on a Mk.IV in the way that many Kirkham owners do and that probably goes for the "continuation" cars as well. Many of the components used were raided from the parts bins of much lesser Ford models.
Nicely built Kirkhams are around the £100K mark in the UK.
Would I swap my Kirkham for one of these AC "continuations" if someone offered? Probably not.
Paul