I’m a little confused. 40C is fairly common in India where I live. My air conditioning works fine here even in relatively high humidity. Is there something special about how a/c units work in the UK? Are they rated for lower ambient temperature or something?
It's less about the AC units, and more about the buildings. In places like Spain and Portugal, white painted outside walls, shading, and shutters on the outside of windows all help keep the heat out. My house has none of that, it just absorbs most of the heat from the sun.
Ah! That explains it. I'm sure if my house were in the UK, I would freeze to death in winter.
UK houses are totally fucking useless for cold weather too.
Maybe the new builds which are just brick skins, but there's plenty of older houses that are built like tanks (I live in one).
There are also plenty of older houses that are built very cheaply and not much good in heat or cold either (eg single-brick-skin Victorian terraces)...
OP probably has a small AC unit with a pipe that you send out of the window. We don't have proper AC over here in most houses, because it's normally only hot a few weeks out of the whole year.
Portable units have terrible efficiency. Unfortunately that is often the only option in apartments.