A foreign based director cannot be prosecuted under the Corporate Manslaughter etc Act because the Act only applies to corporate bodies not individuals.  They could be prosecuted for Involuntary Manslaughter under Common law or under section 37 of Health and Safety at Work Act but first you would need to get them to the court in the UK.  Extradition of people for H&S cases is not always easy.   

See this https://www.independent.co.uk/news/pounds-17m-fines-after-ferry-walkway-tragedy-1270291.html . I believe that the Swedish owners were never brought to book.