Avent do sell teats 0+months (1) 1+months (2) 3+months (3) & 6+months (4) so you maybe able to just buy some extra teats & keep those ones for when babies ready @gemmajoanne

I bought some avent ones but they say +1month @sara-lou

What bottles have you gotten? @gemmajoanne Usually bottles come with the 1st teats ready for newborns, so I'm sure it's fine. You usually then have to purchase fast flowing teats as they get older 3month+ etc