Just keep a lookout for white transit vans in your area.
They'd be either Romanians looking for scrap. I've spoken to a van with these chaps in- very nice, just looking for stuff left out for collection.
I also said morning/tried speaking to two blokes in a transit....they spoke in a accent much closer to the Romanians. Guess which ones I distinctly worried about. It wasn't the former.
Is it worth reporting the latter? Would anything actually happen as really they haven't committed any crime.