I think you might need a space between the border and the next tile. Have a look back at my tutorial and you will see each tile is separated by a gap of one pixel and each tile is surrounded by its own border. Your tiles share a border on each side.
I'll attach my current tile set.
In terms of the complete Dizzy tile set, I have that as a separate IFF,file I think it is too big to load in to reality or I am just too impatient to wait for it to be loaded in. Or it could be the same issue as you have in that the tiles share a border rather than having their own individual border and a space between the next tile. I am currently copying and pasting the ones I want into my tile set using Deluxe paint 4.