I haven't heard of 'half and half' - we don't have this in England - does it go by any other name??

Single cream is probably your closest equivalent in the UK.

In the United States, half and half is a mix of 1/2 whole milk and ½ cream, typically used as a cream in coffee. Half-and-half does not whip, but it can be used in place of whipping (heavy) cream in many recipes for less fat cooking. Its fat content is12%.