It looks to me that those who have the 12th edition of Chambers will struggle with this puzzle. I have found this recent history of the Chambers dictionary on the Crossword Centre website:
http://www.crossword.org.uk/chambers3.html. It says:
"In 2011 the 12th edition of the Chambers Dictionary was published... The main complaint from crossword enthusiasts was that the section of Some First Names had been omitted.
"August 2014 saw the publication of the 13the edition. To the delight of crossword enthusiasts the list of First Names was reinstated."