Hi there, Our room varies between 21-23 degrees most nights. I’ve had my baby in a wonder cool suit, singlet and 1.0 TOG bag. Should I keep the singlet on? He is only 17 days old. Can we sleep with the ceiling fan on?

It is difficult to give a precise answer to questions about clothing/bedding for sleep. Every baby is different.
Red Nose recommends dressing baby for sleep according to the room temperature.
It is not necessary to have heating & cooling on all night, but to dress the baby appropriately.
https://rednose.org.au/article/protecting-baby-from-overheating-during-sleep

Dress your baby as you would yourself - not too hot, not too cold. Feel baby’s tummy or back to see if it is comfortably warm. Ensure baby’s head & face are uncovered eg no hats when sleeping.

An oscillating fan, positioned away from baby can be used during hot months.
https://rednose.org.au/article/how-to-dress-baby-for-sleep