In the UK you'd buy double cream, which is the US equivilant of heavy cream.

The primary difference between milk, half and half, and heavy or whipping cream is the fat content. The higher the fat percentage, the easier it is to whip. Milk has the lowest percentage of fat, resists whipping, and doesn't hold the air bubbles well. Half and half is half milk/half cream, but not enough fat to truly whip. Heavy cream and whipping cream and very similar. Whipping cream usually has some additives in it to stabilize it and usually has a little less fat. Heavy cream is exactly that, cream with a high fat percentage. This is the purest for whipping, but either whipping cream or heavy cream will whip up into lovely whipped cream.