Thanks FoxFifth and related to your answer - One surprise to me when going into iCloud Photos (for housekeeping) and downloading originals to a HD, (to reduce iCloud) storage, was that the downloaded images did not show the original date (EXIF data) but the download date. Probably obvious to most members.
Also if an image was taken as a 'live' HEIC then this was split into two files - one a video, the other the HEIC (lower res than of a plain old static HEIC). That be useful for others to know unless I was doing it the wrong way, I could not see a way of getting the image with the original EXIF.
From now on I'll download the next lot of images into folders with the original M/Y date to know when they were taken.
PS. Storage on iCloud was running out as I did turn off Photos on the iOS devices but 'back up' was left 'ON'. Unfortunately 'optimize' may have been 'ON', so that images in one device were a lower res than those on iCloud. Hence the need to download them and not just back up the device to a lightning drive.