Doesn't that mean the poor exterior insulation may be resolved, in an economically acceptable manner, in the same go in the near future?

I am affraid it will never be on par with a the modern builds (minergie etc) and if you put in a system that would work well in minergie but it is not really adapted for a well insulated 1970s house it might be dissapointing in really cold days.

Minergie or the latest builds are virtually air tight which an old house so they are super easy to warm

Of course, and obviously the facade isn't the only leaky big component, roof and windows come to mind. That's just not the same as "nothing can be done". But of course it's your decision.

Windows are already double glazed, facade definately not roof probably not.

I am willing to upgrade the insulation but I fear even upgraded combined with underfloor heating will not be enough compared to bad insulation and radiators. That's why I wanted to hear some real world experiences, whether an upgrade jump is really worth it in such an old house and if the warm factor will be noticable.