Our best investment was a drop arm canopy over our massive, west facing lounge window. We can still see outside and it keeps the sun off completely all afternoon/ evening /
It knocks at least 5° off the indoor temperature.
Neighbours across the road have put black film over their front window, which looks incredibly odd.
For our morning sun bedroom, I put a sprung pole with a white sheet right up against the inside of the glass and it does make a difference, our blackout blind which sits 4 inches in feels like a radiator without it.
We have a floor standing air purifier downstairs which we combine with a fan on the floor pointing up, which directs cooler air at the ceiling. 24° in my lounge but thankfully little humidity