Information taken from NHS Choices website:
Moving to another country can be an overwhelming experience. Travel arrangements, accommodation and visa or work permit are obvious things to consider when preparing to move, but what about planning for your healthcare?
If you are moving abroad on a permanent basis, you will no longer be entitled to medical treatment under normal NHS rules. This is because the NHS is a residence-based healthcare system.
You’ll also have to notify your GP
You will no longer be entitled to use your UK-issued European Health Insurance Card (EHIC) to access healthcare abroad.
Before leaving for your new destination, it's important to check what health services are available to you in that country. Healthcare systems vary from country to country and might not include services you would expect to get free of charge under the NHS.
In most cases you’ll have to register with the relevant authorities abroad. Once you are registered to work and make National Insurance contributions, you'll be entitled to state-run healthcare on the same basis as a national of that country. However, many countries still expect you to make patient contributions or to join the national health insurance scheme. Use the country-by-country guide for detailed information.