A story I'm entering for a competition has to be in double spacing.
So, does the space between paragraphs have to then be 4 lines,3 lines, or keep to
2 lines which then looks like one continuous piece of writing.
Help would be much appreciated.
I would say 4 lines.
In single line spacing you would put two lines between finishing and the next paragraph. So ignore the fact that you are in double spacing, and still tap in two lines between the end and the next paragraph, which now (doubled up) gives you 4 lines.