Hi, My sons 18 months old, almost 19. He sleeps with two comforters (a jellycat and a more traditional blankie with elephant head). He wears a sleepsuit but our house is freezing!! I was wondering what age is it safe to introduce a blanket? And what materials it should be. And the same for pillows, at what age? I should also mention he’s on a toddler floor bed with a firm innerspring mattress (so feels a little bouncy & softer than normal mattresses).

Most toddlers are unlikely to stay under blankets while in a cot & often when they move to a bed..
If you are concerned about your child being cold, then an extra layer of clothing can be worn under the sleep suit, rather than loose blanket or doona.

Red Nose has the following information about the use of pillows & soft/loose bedding.

Soft bedding is dangerous in a cot and should not be used. Soft bedding includes pillows, quilts, doonas, soft toys and bumpers. Soft bedding may cover the baby’s face and obstruct breathing and/or cause overheating.
Older babies in a cot can be at an increased risk of a sleeping accident by using pillows and bumpers as a step to climb up and fall out of the cot. It is safer to wait until the child starts to sleep in a bed before introducing a pillow or other soft bedding.
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows

** Red Nose does not recommend placing a pillow where baby sleeps unobserved. It is safer to wait until the child starts to sleep in a bed before introducing a pillow. The Australian government states it is safer not to use a pillow at all for children under two
https://rednose.org.au/article/pillow-use