UK fluid ounces
A UK fluid ounce is about 28.41 milliliters, a little smaller than the US fluid ounce of about 29.57 milliliters. So 1 US fluid ounce is about 1.04 UK fluid ounces.
Teaspoon
There is more than one type of teaspoon:
A US teaspoon is 4.93ml: US teaspoon
A UK teaspoon is 5ml: UK teaspoon