During one of our walks at the heath last autumn we noticed some interesting seedheads.   Not recognising it I brought one home and planted a few of the seeds a couple of months ago.
The seeds germinated and are producing seed heads which I've now identified as Thorn Apple.  Apparently it's only found from middle England southwards.   It also states that the plant is poisonous with the seeds being highly toxic and hallucinogenic.   
I think the moral of this story is to look but leave well alone !!