Upon checking the Metadata details under the heading on the right of the Library module screen, it clearly shows the sidecar files as xmp both for the image with adjustments and the rest of the sample for which I have found the xmp files of the same name but have been unable to re-apply the adjustments. The Metadata for my other files without the xmp files in the same sub-folder do not show the sidecar under the Metadata heading.
The only difference between the image with adjustments and those with sidecar files but adjustments not applied was that the former gave a 'Resolve conflict' option against Metadata status. Having done this, status changed to Up To Date, the same as all the other files, yet the adjustments are still being applied.
Given that I know how to find the .xmp sidecar files, I'm now back to wondering how I can re-apply these adjustments to the original images. All suggestions gratefully received.