If you moved back to the UK to resume your residency then I agree totally that you should be entitled to receive FREE medical treatment as soon as you arrive. But at no point have you stated that would be the case, in fact everythng you say suggests the opposite. Which means...
I resume my residency the second the plane lands..Its my right to do so and you have no idea about my intentions to stay..
Of course the situation could alter at which point I could leave at any point and resume my residency here.. No laws broken and I have received that of which I am fully entitled..
I will now give this advice freely to all British expats that are lucky enough to have retired old and young alike..Like me!