Thank you very much for your consideration.
This is how I am already doing it within WL and it works well.
The utility I was looking for was much more straight forward and more or less ‘automated’. No file by file save and no need to create and render from montages. Completely off line.
At present I use the one that Rail Jon Rogut was kind enough to provide which I don’t think is freely available (at least I’ve checked his site and it’s not there).
It’s not a big issue.