I get exactly the same link whether I use the website or the folder on my computer, tablet or phone. They never start with dl, no matter what folder I pick them from - Dropbox latest software(I'm using a computer I bought in August) doesn't give you a public folder, they say that the link does that for you(this is clearly stated in the link to their help page you've just posted) except it does not work!
Here is another annoying little symbol that ought to be a photo:
and an entirely unrelated 'photo' from a different file
If you can tell me what they are Nigel, I'll send you a replacement plug socket in the drive of your choice!
First pic is a welded wheel arch, second pic is of a Ford Capri.
I was able to view your photo by clicking on 'quote', as if I wanted to reply, copying your link, pasting it in to the browser, changing www to dl, removing the img tabs and then open the Dropbox page. I could have then saved your image to my local folder but I knew Nige would beat me to it.
Keep at it and you will get there in the end. I've done screen dumps of each process using photobucket for other members in the past and when you get to a certain place it all seems to make sense and you can work out where it was going wrong.