Following Ounces Recipes in the UK?

Hey all I'm very new to cocktail making and I have been following some recipes from "The Craft of the Cocktail" book I recently acquired.I've noticed that all the recipes use Ounces (I'm guessing American Ounces) but many of the measures in the UK and the one I have at home is 50 ml / 25 ml. When following the recipes do you just use 50 ml when you read 2 Ounces or do you measure it out so it's closer to 60? If so doesn't that make all the UK jiggers etc obsolete?I just thought I could be getting some of the ratio's incorrect if I were using the UK measure that I have.What do other UK Cocktail makers do when all our measures are in ml and not Ounces? http://www.reddit.com/r/cocktails/comments/3e4u3l/following_ounces_recipes_in_the_uk/