Janet Baraclough wrote:
it sounds as if it could be a euphorbia. Nice plants but sensitive
people can get a very unpleasant longterm contact skin rash.
So be careful/wear gloves for the next suggestion; break a stem or leaf
off and see if milky white sap ooozes out. Like cream.

After a bit of googling, I realise - "otherwise known as poinsettia"?
Surely anyone who had been around a shop at Christmas would recognise this
instantly? Mind you, not surprised at one growing wild, as they seem to
just get chucked away each year - surprised it survived the winter, though.

I've just been looking after the MiL's 4 from the past couple of
Christmases, and I know /I/ would like to throw them away now!