Traditionally November is getting a bit late to plant things but here in London I think we have in effect a nine month growing season. It's unusual to get a frost until December or even January. Warmer winters seem to be the general trend and this metropolis of millions creates a microclimate of sorts.
 So it doesn't seem to be a problem planting the hardier specimens around now. I saw these Euphorbia amygdaloides 'Purpurea' in my local garden centre at half price- too good to miss! 'Purpurea' is a selected form of our native Wood Spurge.
 The plant more commonly used in gardens (including this one) is E. amygdaloides var. robbii which has a deserved reputation for being sturdy even in dry shade. Commonly known as 'Mrs. Robb's Bonnet' it's said that the original specimens were bought over from Turkey by a Mrs. Robb in her hatbox.