datura

Cucurbita - a pumkin plant if not a squash

Brugmansia aka Angels trumpet.

Not hardy, more of a half hardy bedding things. Birds drop seeds and they grow easily, Highly poisonous, sap, leaves seeds etc. so not good if kids are around. Best to handle with gloves and bin.
Or if no kids around, it can be left if required, but pods are very prickly! Worth removing whole plant before it seeds, although the seeds may not survive over winter outside

Thats scary they look so similar?

I'd go with Datura

Yes! That is a Datura, I boughts some seed this year and grew them Ha! Flower reminded me of Bineweed and Yes! Very Poisonous I found out, have enjoyed the plant but will not grow it again, Oh! It will dye off in the winter but if you want to keep it going and you have a conservatory it will over winter in there.
Jackie

Now I am confused I thought Datura leaves were more even and not spiked as this picture shows?

The usual type grown for summer flowers does have plainer leaves.

Brugsmansia- just id thought id throw that into mix!

check out this page on GoY

http://www.growsonyou.com/shop/product/36405

Its definately a Datura.
Probably a Datura Metel La Fleur available from Thompson & Morgan.
Only the flower colour is different - lilac.