The third country to have a major role in the origin and history of the JONES surname is England. It is the transliteration of the Welsh to the English during the transition period produced by the Act of Union 1536 that seems to be the main factor. [Certainly other factors also involved.]
My own posts that give some background to this topic are:
1) Early English Records and the Jones Surname, March 21, 2011
2) Ancient Petitions A Transition Period, April 18, 2011
3) The First JONES Surname in English Records, March 21, 2011
4) Jones Surname 1273 - 1500 in England and Wales, May 17, 2011
5) Jones Surname in England and Wales 1500 - 1700, June 2, 2011
All posts can be found at http://thejonesgenealogist.blogspot.com . Other subjects and themes can be found here also.
England and the surname JONES, one of the three countries that are key to the geography (g.). Those who have an interest in this theme, please post in the comment section.