Cooks in the UK weigh ingredients, using metric measurements (some still use imperial pounds and ounces, but that would confuse the issue even further, so we’ll stick to metric). In the US, cooks use decidedly less precise measures, and virtually everything is measures in cups. Occasionally meats and produce are listed by weight measure (pounds), but otherwise it’s all cups.
This creates a problem for conversions, because different ingredients have different volumes. So 150g of currants, for example, converts to 1 cup, whereas 150g of caster sugar measure 2/3 cup, and 150g of puffed rice cereal measures 6 cups!
The solution? I have bought a cup measure, and for recipes on this site have used it to measure my weighed ingredients, to give as close a conversion as I can. If you want to convert ingredients in other recipes, here is a basic conversion chart, but be aware of differences in volume and use your judgement.