You need to look at the gov.uk overseas health pages Dinahmo.
"Some former UK residents do not have to pay for NHS treatment when visiting England. This includes:
UK war pensioners
UK government employees
UK nationals living in the EU on or before 31 December 2020, once they have a registered, UK-issued S1."
If you ring the Overseas Team in Newcastle they will confirm it for you. You need to carry your S1 form when in UK and ring them if the hospital is not conversant with the guidelines.
A drop in the ocean in the great schemes of things....but replicated by how many more

