I am afraid that the requirement to vote in a UK general election is that you must be a British citizen. This situation is not unique to the UK: many countries only allow their citizens to vote at general elections, and linking citizenship to the right to vote is not unusual. The UK additionally allows qualifying Commonwealth voters and Irish citizens, resident in this country, to vote at general elections. This position reflects the historical ties between the UK and Commonwealth countries, and the historical ties and reciprocal arrangements between the UK and the Republic of Ireland.
Currently, EU citizens resident in the UK can vote at elections to local authorities, devolved legislatures and the European Parliament, but you would need to apply for British citizenship to be eligible to vote in general elections. Information on how to become a British citizen can be found here: https://www.gov.uk/becoming-a-british-citizen.
British citizens who move abroad remain a vital part of our democracy, and it is important that they have the ability to participate. Indeed, expats retain strong links with the UK. They may have family here, or plan to return here in the future, and modern technology and cheaper air travel have both transformed their ability to keep in touch with their home country.
I am therefore pleased that the Government is committed to introduce votes for life, scrapping the rule that bars British citizens who have lived abroad for more than 15 years from voting. The Government is supporting the Overseas Electors Bill, introduced as a Private Members' Bill by Glyn Davies MP, which is currently in Parliament and which would remove this rule, and I believe it deserves cross-party support.