- 1 You work in Greece and contribute to IKA.
2 It is provided under an S1 form from your country of origin, e.g. in the case of the UK you are a State Pensioner.
3 You have an IKA pension, and it is your main pension if you have pensions from more than one country.
Main here does not necessarily mean biggest but based on longest contribution. For example I have a UK State Pension and an IKA pension. My UK State Pension is based on over 30 years NI contribution in the UK. My IKA pension is based on a little over 13 years IKA contribution in Greece. I get healthcare, therefore, through an S1 form issued by DWP in the UK because my UK contributory years were the longest, i.e. the UK is taking responsibility for the cost of my healthcare.
There is strong evidence that healthcare for UK State Pensioners provided through an S1 form "will" continue after Brexit in the interim agreement reached between the EU and the UK a few weeks ago. As far as I can see that would include people who are resident here now but have not yet reached UK State Pension age. That agreement also shows that preserving the right to reside after Brexit "will" be easiest if you have a Permanent Residency Document. I put "will" in quotes because that interim agreement is not certain until a final agreement is reached.
I repeat what I have posted earlier; physical residency and tax residency are not necessarily the same thing, although there is a clear indication that they are supposed to be. There are plenty of people here with a Permanent Residency Document but who remain tax resident in the UK. Getting a Permanent Residency Document does not, at least at present, commit you to being tax resident in Greece. Obviously that could change at any time.