It's best to use full-fat cream cheese for the icing - it offers the best taste and texture. In the UK, cream cheese comes in a tub and if you find it has a lot of water around it when opened, it's best to drain that off. If you prefer, reduced-fat cream cheese will also work and be very tasty. However, the consistency of reduced-fat cream cheese can really vary, so add it to the sugar bit by bit until you have a spreadable icing.