How to prevent my house from getting hot?

In this part of the world the climate is cool temperate, so outside of places of work etc. not many people have AC. However, we have a heatwave (in relative terms) at the moment with temperatures around 25 at night 30+ during the day. This sort of think usually only lasts from a few days to a couple of week and doesn't even happen every year. Options short of multi-room AC:-

1) Domestic portable AC unit. c. £300, + might need a kit to reduce inefficiency where the exhaust is directed out of the domicile.

2) Air cooler. Some use ice packs / water droplets for the cooling function. Not usually near as good as proper AC, but approximately 1/3 of the price.

3) Multiple fans, arranged for good throughput of air.

4) Tower fan. Get a bucket or large bowl, fill with ice and put it in front of the fan. A bag of ice should cost no more than a buck/pound/quid. Inefficient, but much better than nothing if you have easy access to ice.

5) Hanging wet sheets / clothes *does* sort of absorb heat, but.... unless you have very good ventilation it will make things differently bad. You might lose a bit of heat but gain a bunch of humidity.

You can hang the wet bed sheet or another long cloth hang inside the house.It decreases the hot for a little time.

We use these things called fans

Let less light in, don't use the oven, don't use the microwave, don't watch TV, keep your computer turned off, and use a fan. Or, you could just buy an AC. They come in all sorts of sizes and price options.

Don't turn the oven on and keep the windows open. That's about all you can do.