Yes, UK is “only” 40 degrees or whatever Fahrenheit is.
But you need to remember, we’re a very traditionally built country with a lot of houses being from the 30’s-50s with pure brick construction and insulation. For example, a lot of US homes have internal stud walls made from wood partitions and plaster board. In the UK and many other places in Europe, our internal walls are solid masonry (cement, brick, plaster)
In addition, 99% of homes do no have air conditioning. The country is very northern so we’re built for winter and not summer.
Someone is comparing Texas summers to the UK, lol. UK is no where close to the equator compared to the whole USA. Even more so we are not even further south than Canada.
We’re also a very densely packed country and don’t have roaming open ranges or nothingness like the USA. Every corner of the UK is packed, so again this is completely different than what most of you have experienced.