Jon, checking a couple of your "later articles" I assume they're all by Bernard Lundberg. I'm not aware his impressive articles were ever published as a collection.

The original construction series by Robin Dyer was easy to follow (must have been as I made one) but Bernard's research adds markedly to the authenticity of the model. For example ME vol 170 (3946) repeats Dyer's confession that he had no information on the front axle; Lundberg's article corrects that.

I'd recommend obtaining a copy of ME 170 (3944) as this contains an informative but very short article by Lundberg "Clayton Wagon General Notes". In the same issue, there's an article about building a Clayton with twin rear axles – though never produced by the works.

There are a few significant shortcomings in the original design. Main one being that the main drive gearing is too fast. My failing memory is that at least one remedy for this was published in ME, but it wasn't elegant or of course, prototypical.

“Hopefully someone may come along with”
Are you hoping someone will scan them all for you or hoping you’ll receive a list of references? If the former, there’s copyright infringement to consider. If the latter, you might use one of the online indices. As you probably know, there’s always back nos of ME on Fleabay.
The hand pump in the water tank will provide adequate boiler water when stationary.
IMHO what spoils many model Claytons is that builders have not put the compound curvature on the front apron. Fairly easy if you get a large lump of soft wood & shape it as per design. Cut in holes for clamps, anneal the brass sheet and bend to wood former. Then with piercing saw keep cutting ‘darts’ (Vs) and with more annealing, tap down to form compound curve. Soft solder into joints & after wet & dry it’s ready for paint.