I know this may sound nit-picky, but I can probably tell more from the original photos than from the latest group.
![frown frown](/images/graemlins/default/frown.gif)
The sample shown in the latest photos looks like it was unraveled off of the head of a weed-eater.
![wink wink](/images/graemlins/default/wink.gif)
Ideally, one should take a reasonably close-up photo of the plant in its natural state of growth (say, from 5' away) which shows "how it grows" in relation to its environment.
Then, gently isolate and extract an individual plant (or pair of plants if connected) and spread it across a contrasting background - with a coin laid next to it for scale-reference - and take a closer-up photo (2') of the entire plant; and possibly an even still closer photo of the leaves which shows how they (2 or more leaves) connect to the stem - and also snap a close-up of any seed-head formations.
These, and many other visual or sensory clues, are used to assess a plant's identity.
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edit: Just now remembered that you're in the UK, which may explain why your plant doesn't resemble anything with which I'm familiar. Still, some photos using the above guidelines might help with the ongoing investigation.