Usual practice is to wait for the fronds to die back, then pack the top of the trunk with fleece and wrap the whole thing in fleece too. If the fronds don't die back, you have it in a sheltered enough spot not to have to worry about it. I grew one in Bath years ago in a very sheltered, shady, courtyard - it never lost its fronds, even though there was sometimes a light dusting of snow sitting on them, and it was never given any protection, so it does depend on the microclimate surrounding the plant.