its a Galtonia albacans I think. also known as summer hyacinth. there is an all green form too. var . veridis

Hhmm. Galtonia candicans and the green one is Galtonia viridiflora

yep candicans, [don't know where I got the word albacans from arghhh!] but I have seen a label saying var veridis, though you are right owdboggy my book says viridiflora.

I am loosing the plot!

There is also one called G. princeps, but not sure what the differences are between it and candicans, they are both white. I have a lot of the candicans, self seeds all over the place, but the viridiflora is now down to three bulbs and struggling.
There are some in one area white are not pure white nor the green of viridiflora, rather a pale green, off white sort of colour. Not sure what they are.
Seed sown in Spring, takes about 2 years to reach flowering size.