Hot Summer in London

It's been extremely hot recently in London. I have a boiler next to my room which is on all year round. In winters, it's perpect, no doubt, the whole flat is amazingly nice and warm. However, in the hot summer, it's unbearable. I couldn't stand it. Cooking and showering makes the flat even more horrible. The hot air has no way to get out of the flat. What's more, the sunshine is through our windows every day, which makes it even worse. Kai is in his nice office every day which has an air con while I am at home all day every day withstanding the hot air as well as the constant noise coming from the construction site nearby. It's not advisable to get an air con at home, as the summer is amazingly short in the UK. Whereas how can I stand the hot weather in the short summer!!!