Hi, I am constantly confused about the number of blankets baby needs etc. At the moment the room temp is 23 degrees he’s just ina singlet. I’ve wrapped him in a cotton swaddle with a single blanket on top. Just woke him up to find his entire back soaked with sweat. This has happened with Muslin swaddles as well.

There are no specifics about the number of blankets to use or what to dress baby in.
Like adults, babies are all different.
However, Red Nose has the following information.

How to dress baby for 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.

Always remember to remove head coverings for sleep and ensure baby is positioned with their feet at the bottom of the cot – and if you’re using sheets or blankets, make sure they are firmly tucked in to prevent baby from wriggling down and overheating.
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

Can we say how many blankets to use for baby?
The simple answer is – No. Red Nose recommend that rather than state how many bedclothes can be safely placed on a baby, parents can work out the amount of bedding to be used after considering these factors:

Room temperature where baby is sleeping
How hot does the baby feel? A good way to check baby’s temperature is to feel baby’s back or tummy (don’t worry if baby’s hands and feet feel cool - this is normal).
Whether the baby has a cold or infection or another special need.
Consider how many layers that you as the baby’s carer are wearing comfortably.
https://rednose.org.au/article/bedding-amount-recommended-for-safe-sleep
https://rednose.org.au/article/how-much-bedding-does-baby-need

If you are concerned about him being very sweaty, then be in touch with your Health Professional.