The information requested is not regularly collected. However an estimate for 2002 of up to 73,000 foreign HGVs was made from a one-off survey of foreign vehicle activity.
It was announced in the Budget for 2008 that the Government will be running a new foreign vehicle survey, scheduled to take place in spring 2009.
Annual data on the total number of trips made by foreign registered heavy goods vehicles travelling to mainland Europe from the UK can be found in Table 2.1a of the publication Road Freight Statistics 2007 available in the House of Commons Library and on the DfT website at:
http://www.dft.gov.uk/162259/162469/221412/221522/222944/28584011/04_RFS_2007_Section_2.pdf.