Comment For Game of Thrones, it's also convenient (Score 1) 516
Game of Thrones is mostly being filmed in Belfast due to good facilities, tax breaks and partial funding from Northern Ireland Screen. During casting they specifically looked for local actors. There are a few exceptions such as Sean Bean and Peter Dinklage, but most of the other actors (especially the children) are British. One of the most important reasons is availability: when you're planning a multiple-year series you don't want to engage actors that are likely to drop out due to other jobs. Actors already living in Britain will be far more likely to be available for subsequent seasons than actors based in Hollywood.