The UK Government has issued a statement today that British nationals who move abroad on a permanent basis will now lose their entitlement to free NHS healthcare on visits to the UK. Since the NHS is a state healthcare system providing entitlement through residence in the UK, those British nationals who move abroad to live now that the Transition Period is over will not be eligible for free treatment in the NHS when they return on a temporary basis to the UK. The British Government says:
UK nationals living and working in EU countries, Norway, Iceland, Liechtenstein or Switzerland on or before 31 December 2020 and their family members may be eligible to use NHS services without charge. You may be asked to provide evidence of your residency. Please check with the authorities in the member state in which you reside for further information.
If you are a UK national and move to the EU, you should not expect to be able to use NHS services for free when visiting the UK unless you have an EHIC, PRC or S2 to show your healthcare costs are funded by the EU country in which you now live, or another exemption applies.
You should take out appropriate travel insurance when visiting the UK, as you would when visiting any other country. Any treatment you may have to pay for will be charged at 150% of the national NHS rate.
Some former UK residents do not have to pay for NHS treatment when visiting England. This includes UK war pensioners, UK government employees, and UK nationals living in the EU on or before 31 December 2020.
You should check before travelling to the UK whether you qualify for an exemption from charging or will be required to pay for your treatment.
If you return to the UK permanently and you are ordinarily resident, you will be able to access NHS care without charge.
There is more information from GovUK HERE about healthcare for anyone entering the UK as a visitor.