Thanks Kitz I'll give it/them a try later today
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Well I tried "Advanced Batch Converter" but I could not find how to change the setting from Pixels to MM, which I would really need.
After selecting an existing .jpeg file which the size was 1514 Pixels, I then selected the batch mode for a load of files, selected change all to 1514 Pixels, but it also changed the format to .bmp of 3200 pixels (approx) obviously I should of also selected the format I wanted.
But at least it does seem to be able to do what is required, just needs a lot more careful setting-up.