"Life expectancy was lower not because of lack of central heating - but because of lack of modern medicine and no NHS."
Warm housing was a factor too.
Why do you imagine fuel poverty is a problem?
Hint: it's because being cold for extended periods is bad for your health.
"Yes it's a shame no one has babies in Russia or Mongolia isn't it?"
What can that possibly have to do with whether a woman in England should bring a baby to an unheated house in winter? 
Do you think the tribes in Mongolia don't heat their yurts?
People who live in cold climates spend a lot of time making sure they are warm.
Oh, and PS I said it would be like going where you knew there wasn't enough food, ie where you knew that basic needs like food and heat would not be adequately met.
A baby can't tell you they are cold, they can't move around to warm up, they can't lie on the floor and kick their legs and roll over if they are wrapped up like a Michelin man, which is about their only fun at that age.
What is the point of all that for a completely unnecessary trip?
I'm the parent who is always getting remarks about not keeping my baby warm enough, and I would stay home. I don't get how it can possibly be unreasonable to want to keep your baby warm.
"DD was considered to be at risk of SIDS so we stick like glue to the recommended room temp range of 16 - 20 with an optimal temp of 18."
Keeping a house that warm frequently requires additional heating at the moment 
You are telling the OP she is U to take her baby where she will likely have to sleep in colder temperatures than you deem apprproprite for your baby.