Of course as soon as I ask a question I find the answer – just like going to the doctor when you immediately feel better before you see him! In case anyone searches for this in future I will describe how for the record.
When using Styles:
In the Paragraph Style, Basic Character Formats, Leading: make sure the value is not in brackets, if it is auto leading applies. Consciously choose the value and the brackets will disappear showing that autoleading is off.
When using In-Line Formatting:
Check the leading value in the ribbon, this is in the Paragraph Formatting Controls and has the two ‘A’s on top of each other with the double-headed arrow beside it, if you hover it will show ‘leading’ in the tooltip. Put the cursor in the paragraph you want to check, look at the leading value in the ribbon; if the value is in brackets, as with the Paragraph Style, it means autoleading is switched on for the paragraph in question – if you display the selection dropdown you will see Auto is selected in the list. You can turn it off by selecting a specific value.
Hope this helps someone in the future,
liz