Resizing was all down to a great steer from your online forum guidelines Danneaux - plus referral to the Apple community.
For anyone else struggling to resize on a Mac it's actually dead simple:
- Export the image from Photos to another location on your machine
- In the Export window click a dropdown to reveal "Custom Size" option
- Choose pixel numbers for height and width to give a file size the Forum will accept (<512kb I think)
- Attach the resized image in it's new location on your machine to your post.
Of course with all things digital you still require and element of perseverance and luck!
