You can make a simple a.c. by putting a rack with wet towels in front of a fan, tho it loses effect once the humidity in you house gets higher.

San Diegan here. Beach. That’s what we all do. Pool works too. And of course AC.

Get as much cold air inside overnight as possible then close all the doors and windows a little after sunrise. If your house is well insulated it’ll keep it relatively cool until after lunch. Also, keep the blinds closed on the side of the house actively getting sun.

Light weight or moisture wicking clothes.

Fans. Lots of them.

Damp washcloth on your neck or a spray bottle to mist yourself. If you want to step that up, put the washcloth in the freezer for a bit then wipe your face/neck down.

If you have a basement, spend time on it. It's much, much cooler below ground. The earth is a great insulator.

Go out to movie theaters, malls, or other public spaces that have AC. Visit public pools, beaches, etc.

Get a desktop. Despite what people are going to tell you, laptops are not an optimal choice for gaming. It usually always comes down to the fact that those little tiny cases are not efficient at removing heat.

Over heating and under performing is the typical story for gaming laptops.

You want to get some nice blackout thermal curtains for any windows facing south. You might actually need 2 sets of curtains to fully block the sun. I've noticed a big difference this year since I added a 2nd thermal curtain on top of the 1 I had. Unfortunately that only helps so much and as long as it's unbearably hot outside you're going to see the heat increase inside as the day goes on. At night open all of your windows and run fans to get as much airflow as possible while it's cooler outside. In the morning close your windows the minute the outside temperature is the same as the inside temperature. As long as it's cooler outside, the windows should be open.

If you're without an ac in Europe I highly suggest getting a simple window unit for your room. They are easy to install. Be sure to seal your door so the air doesn't escape. Portable ac units are known to be very inefficient, be wary of those. Cold showers help in extreme circumstances. Block all sources of light. Blackout curtain or just some covers over the windows. Keep humidity below 60% if you can, dehumidifiers will help but larger ones will rack up your electric bill quick.

One thing not mentioned, ice.

Drink water with ice to physically reduce your body temperature. Wipe yourself with ice packs. Eat ice cream and frozen popsicles.

I recommended if you have a two floor house put a window fan sucking the air out on the top floor. It makes a huge difference.

External keyboard and mouse on laptop.

Air conditioning definetly needs to become a thing in the UK some company is going to make a killing if they lock it down.

Air conditioners are the norm here so it is no problem indoor, and outdoor well we were born in it molded by it

If you're out and about, I recommend light clothes, something to keep some sun off (EX: a hat or an umbrella or parasol), and a folding fan (even if the air is hot, the breeze is still somewhat nice)