Hi Neil, great to hear from you once more, well all I can say is the chap who runs our local Engine Overhauling company looked at one or the Piston Rings, and explained that there was a very sharp ridge on the lower edge , and even demonstrated it by cutting a piece of paper with it!
This he reckoned was coursed by “Fuel Wash” , this of course breaks down the surface lubrication, causing rapid excessive wear.
Actually, when he checked for Bore wear, it was lass the 0.002”, the Pistons themselves looked to be in pretty good condition with only minimal surface marking.
When one of the original Piston Rings was placed into one of the Bores, a gap of around .0062” was found!!!
My own feeling is the just maybe, the Piston Rings May have either been the wrong ones originally fitted( Not checked in the Bore on original build, as of course they were already fitted on the Pistons)
Of of course, they may have been produced from a substandard material.
During my research on Solex Carburettors, I discovered that my Lanchester had been fitted with one that would have been fitted to a Commer, and was of 1950’s vintage, probably changed when the original Thermostarter type expired .
This was a Solex 30 AHG , the correct one is a Solex 26 AHG, I am actually bidding for a 20 AHG Float Chamber assy, this hopefully contains the correct Jets.
At this point in time, I am mid way in completely re- building the Engine, I have to say, that having re-fitted the Pistons in the Bores with the correct Rings now fitted( Approx a .0016” gap

) there is absolutely no movement of the Pistons in the Bores.
I’ll let you know how I get on when I know more


Cheers Al