This is a very quick post and is particularly for Clare who asked about converting the American cups into british grams and ounces. You can actually get a set of the cups from most decent supermarkets baking aisle - we got ours from Asda for less than a pound. Alternatively just use a cup (not a mug obviously, just a normal cup) and guess - the cookies can cope with slight variations to them, the originator practised with different combinations so don't stress too much!
If all else fails and you really want to be very very precise - try this
the original recipe can be found here
which uses a 1 quart jar to make the cookies, last year I used a shop bought storage jar (which was way bigger and took almost double the recipe LOL), this year I've used the larger coffee jar from Douwe Egberts which takes 3/4 of the recipe.
Hope this helps!