More people in the UK think immigration has a negative impact on society than a positive one, according to a YouGov survey for Sky News.      In the first general election since Brexit, all the major parties mention migration in their manifestos. Both the Conservatives and Labour are placing promises to tackle illegal boat crossings high on their list of promises if they get into Number 10.     So what do voters think about immigration and how could it affect these elections?  Host Niall Paterson is joined by Sky News’ community correspondent, Becky Johnson, who’s been speaking to voters in Swindon about their views. Plus, economics and data editor Ed Conway digs into the statistics to reveal exactly how big an impact migration, both legal and illegal, has on the UK.     Producers: Emma-Rae Woodhouse  Podcast Promotions Producer: David Chipakupaku   Editor: Philly Beaumont