Looks like either an Allium or perhaps an Agapanthus. In either case look at the question asked on Allium a couple of days ago to see what to do.

Yes, that'san ivy seedhead. Black is it's natural ripe colour. A very important food source for the wildlife.;

Never thunked of that. Yes could be unripe Ivy berries. Should have recognised it, we have gillions of them and every one produces a seed which germinates and grows.

Yes, they can be rather rampant!! In the summer the 'hedges' of them just buzz with insects, which is rather nice.