My baby’s room faces southwest and gets quite warm during the afternoon and stays that way into the middle of the night (23-25 C). He’s sleeping in a Bonds Coolsuit and 0.2 tog sleep sack only. We don’t have air conditioning to cool the room down but have a fan to circulate the air. Is there anything else we can do? Bub can look a bit flushed and feel slightly sweaty at times.

Red Nose does not recommend a specific room temperature, rather you dress baby to the room temperature.
Overheating (hyperthermia) can be a risk for babies (as well as hypothermia)
Babies regulate their body temperature via their head & face, so it is important, that baby’s head & face remain uncovered.
If baby is waking & you are concerned that they may be hot (feeling back/tummy or redness of face) then you can remove layer of clothing/bedding but still keep head & face uncovered.

Red Nose has the following information.
Dress baby for sleep and add/remove lightweight blankets to ensure baby’s back or tummy feels comfortably warm to the touch.
https://rednose.org.au/article/bedding-amount-recommended-for-safe-sleep

Babies control their temperature predominantly through their head and face. This is why we recommend that you put baby to sleep on their back with head and face uncovered.
Red Nose does not recommend a specific room temperature for baby’s sleep. This is because there is no evidence to show that maintaining a specific room temperature prevents sudden infant death.

As long as baby is put down to sleep on their back, and that baby is dressed appropriately for the room temperature – not overdressed or under dressed – with their head and face uncovered, you can feel reassured that you are protecting baby from overheating.
https://rednose.org.au/article/how-to-dress-baby-for-sleep

It is not necessary to monitor the room temperature or to leave the heating or cooling on all night, as long as the baby is dressed appropriately for the room temperature: Dress baby as you would dress yourself – comfortably warm, not hot or cold. A good way to check baby’s temperature is to feel the baby’s back or tummy, which should feel warm (don’t worry if baby’s hands and feet feel cool, this is normal).
https://rednose.org.au/article/protecting-baby-from-overheating-during-sleep
https://rednose.org.au/article/room-temperature
https://rednose.org.au/article/what-is-a-safe-room-temperature-for-sleeping-baby

A fan can be used, as long as it is not directed at baby & is not able to be reached by baby.