A sensible landlord would recognise that yes but only if they got to keep the air conditioning system. Realistically though the tenant would probably want to take it with them when they left after all they bought it. And the landlord might not want the owners to be on them to buy it off the tenant when the tenant leaves.

I wish I could upvote this 100x.

Yes because the job of the refrigerator is to extract heat from the small area and dump it out the back. An air conditioner is the same thing but it is designed to extract heat from the entire room and dump it outside.

The problem is unless you have ducted heating all that's going to do is cool one room. UK homes aren't built with ducted heating. So the best you can get away with is one room cool and everything else is still unbearably hot. All of which is assuming that the landlord is ok with me punching sodding great holes in the wall. Even for people who own their own homes the cost isn't worth it, it's incredibly expensive to buy an air conditioning system in the UK and then literally no one knows how to fit them. Isn't just a matter of buying one.

Not the type you're thinking of. We have windows that open like doors rather than the American style guillotine things, which have always struck me as inherently unsafe, but I suppose it does have that one benefit.

Produce Co2_ as in the electricity used? And windows open?

300% reduction would mean you no longer pay for heating and instead get paid twice as much as you used to pay