I'm not that old, but I used to live in a house with an outside toilet across the yard (WC not ash I hasten to add.) People managed.
An en-suite means the bedroom will be smaller. And not very useful if other members of the household can't use it for showers etc. So I wouldn't bother.
I've made 4 bad house purchases, because I have always been a bit of a naive idiot. But in the end 2 of them turned out to be places where I happily raised a family. You just don't know how life is going to turn out...
Btw, IMHO it's not govt regulations that will be the main driver for people to save energy. Among other motivating factors, it's the increasing price of fuel which we are likely to see in the future. Maybe not in my lifetime, as I am old, but soon, and depending on what age you are, you will probably live to experience it.
Also, the emphasis on insulation at the expense of ventilation has given rise to terrible black mould problems in many dwellings.