The report itself is here:
Fossil fuel emissions have rapidly worsened European heatwaves in just a few decades
Just weeks after a severe heatwave that broke all-time May records, Europe is experiencing another major heatwave that is breaking June and annual records. This is particularly remarkable given that June is not historically the hottest month in Western Europe. Across France, Germany, Italy, Spain, and southern England, temperatures are reaching 5–12°C above seasonal averages, driven by a persistent high-pressure system. This pattern has transported hot air from North Africa into the region while also bringing clear skies and strong sunshine, which have further intensified the heat.
There are semireflective films you can install on the outside of the window to keep more of the energy out. Just needs some mild soap water and a simple flat tool to install. You can get them in different strengths, i.e. you probably want the mildest option for windows you want to look out of, but max strength for your bedroom (which you want to be dark anyway).
Aware of those but we plan on getting new windows soon anyway. They also seem to cost a fair bit. Covering all our windows would cost many tens of pounds, maybe even over £100.