Overseas Travel and Tourism: Nov 2007 / ONS, 16 January 2007
PDF - http://www.statistics.gov.uk/pdfdir/ott0108.pdf
"...With the enlargement of the European Union in May 2004 and again in
January 2007, there is considerable interest in the number of visits to the
UK from these accession countries. From 25 April 2007, additional
information on the enlarged European Union is provided in addition to the
regular series."