Heatwave how to sleep?

Okay so the uk is having a massive heatwave atm and obviously because we’re not used to it, our house isn’t equipped to deal with it. Now I have this huge about 6/7 foot window which is basically an entire wall. Only a very small tiny square of it opens and even then not a lot. I can’t get blinds because it’s an awkward triangle shape😒 my mum doesn’t let me have my fan on other night for safety reasons which is understandable. ( tbh it’s quite a shit fan anyway ) Lately I’ve just ended up sleeping in the corridor so I can actually sleep. But y’all this heatwave is going on for another MONTH at least! I can’t keep sleeping on some hard corridor with only some blankets to lie on! Please I’m begginggggg for some ideas to help me!!!!