@KayT Mostly this one
https://activewindowfilms.co.uk/products/30-lightly-reflective-mirror-window-film
There are 2 windows which have a different, more reflective film on. One of them is blown already so I wasn't as worried about blowing the glazing panes (which is what made me opt for 30%, to reduce the risk) and the other is exterior. The exterior is by far the most effective. It reduces the light more but it's like there's no window in the room at all, it's so weird when the sun's on it and you just can't feel any heat from it