Gareth Southgate, Ross Kemp and Lorraine Kelly are among the stars urging the public to take part in the UK’s biggest-ever thank you party as part of Queen Elizabeth’s Platinum Jubilee celebrations. National Thank You Day will take place on 5 June and organisers are hoping to break a British record by getting more than 10 million people to join in with the celebrations as a thank you to both the 95-year-old monarch and to each other by getting together with neighbours for a Big Jubilee Lunch. Businesses including the NHS, National Lottery Community Fund, the FA, the Scouts, the Church of Engla…