I note you live in Berkshire, where I know you can get some pretty cold temperatures. It all comes down to the micro climate where its planted, really. This is the hardiest variety of Arbutus - as long as its not planted on an exposed hillside facing north, north east, nor in a frost pocket, it should be fine. Best if you can provide a little protection in its first winter though. Although what I'd really like to know is what you think is a 'typical' British winter, lol - winter here varies between mild and wet and freezing cold, so you can never tell quite what we'll be getting in any one year.