Although it's been around the 28-30C mark (83-86F) the past few days, the nights have been as cool as 16C (61F) so it's been OK.
What I fear is that it's going to stay warm overnight the next few days, certainly feels like it will tonight. I've just been tacking up the solar control film (aka RAF surplus plane cover material. Silvered one side, low IR emitting the other) over the bedroom windows which catch the afternoon/evening sun in the hope of keeping it cool enough to make sleeping bearable. It also means that, as the 'film' is opaque, I can leave the blinds open tonight to let some breeze in but keep the 4:30 AM daylight attenuated enough to not wake us up..
I keep on pondering some A/C for the rare hot periods that could be used as an air source heat pump in the cooler months, but with a Victorian end of terrace property I've problems with siting the outdoor parts. Either they would overhang the back gardens of my neighbours (who I'd need to tap for access and agreement) or I have to plumb through the typically awkward Victorian construction to take it out to the side by my back garden. Either way, I never get around to planning or deciding and put it off until next year's hot spell gets me thinking about it again.