The first step to voting in any election in the UK is to make sure you are on the electoral roll or register. You can register to vote up to 12 working days before a general election. There have been numerous problems around postal voting in recent elections not least May's European elections when scores of Brits in the EU saw their votes go uncounted. British residents living in the EU have since been warned by local councils that proxy voting would be more reliable. Their application for a postal vote must arrive 11 working days before the poll - by Wednesday, November 27th.

Source: The Local November 26, 2019 09:45 UTC