One of the few things I like about Word 2010 & 2013 is the naigation pane. However it highlights issues with Heading style that make the TOC a nightmare. I don't recall the issue occurring in 2003 etc

In the Picture Heading Style 2 & 3 have two blank rows in the Navigation Pane because for some reason the style hasn't followed on to Normal properly or user error. Often seems to occur with insert-Break on a Heading where Word. for some reason only know to the fool that designed this bit, leaves the style attached to the break line.

How do I find single empty lines with a style attached. I used to know the word regex for ^$ but can't find it .

Could you tell me what it is. Ta

You could use a wildcard Find/Replace where you specify the Find Style for whatever heading you're interested in, combined with:
Find = [^13]{2,}
Replace = ^p
This will delete any empty paragraphs in that Style after the heading. Of course, if Style definitions were being used properly, this would most likely not be an issue, as there generally isn't a good reason for having empty paragraphs between headings and the text to which they relate.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thanks I'll give ita go.

Using it properly maybe. Expecting casual users to keep up with the changes not as such.

Word has always worked with Styles (i.e. for over two decades). I still have a reference manual from 1993 describing their use ...

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Ok hence the MVP in your title

I keep getting documents to review from people who haven't read he manual and keep hitting enter twice after a Heading cause that's how they've always done it.

Happy for you to convince them otherwise.

Your solution didn't work as that finds ^p^p not ^(Beginning of line)^p with a style

I thought the problem was with situations where people "keep hitting enter twice after a Heading". However, if you've also got preceding paragraphs is the same Style, you could use:
Find = [^13]{1,}([!^13]@)[^13]{1,}
Replace = \1^p

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]