Stop Excel for Mac (2011) continuing formatting from last cell entered?
Found it! It's a setting under Preferences &gt; Edit: 




  Extend data range formats and formulas




Misread it as "date ranges" on the first trawl through preferences. Turning it off stops this happening.





The comment about formulas seems to only mean that it doesn't fill empty cells with formulas when it thinks it's seen a pattern. After turning it off, it still does other automatic format adjustment e.g. incrementing formulas copied across a range: