Is it a weed? Or is it not a weed?

My first job at Nature's Haven today was to plant the jasmine plants under the newly erected arch. They were grateful for a final planting place at last, having had a trip to Hampton Court in July and been in pots ever since. Then it was on to weeding the big bed, and trying to work out what was a weed, and what wasn't. After all, a weed is just a plant in the wrong place. The brambles still making an appearance are definitely weeds, as are the thistles. As for the rest, we just made it up as we went along!