The .com thing isn't the point I was thing to make. Simply adding UK to the end of the top $ 2 word search term in my niche seems to switch off Panda and Penguin and what is returned is 90% what I would have expected for <<search term>> and <<search term UK>> before Panda.
The point is that it is a term by term, phrase by phrase thing.
If you have been affected, unless you have nothing to lose, I would go softly softly. I certainly wouldn't remove a word from one of my sites entirely. Also if I wanted to reduce the density of a particular word I would favour changing it for a range of synonyms or close semantic match words rather than remove it altogether. I don't buy that Google is now adding up synonyms and the search term and penalising for the cumulative.