Did you plant any gourd/squash of any sort?

That was my guess as well.

'Loads of these coming up'. So I don't think it's a squash. Plus the true leaves don't look right. Could we have another picture taken with slightly more developed true leaves and also a scale? An id doesn't immediately leap out at me as being one of our common weeds.

Hopefully this will help.
Basically I had a number of flower seed packets really out of date.
I put them in Mid-May around the bigger established plants already there.
So now IâÂÂm wondering if its weeds or the flowers finally coming to life.
The pattern of them is consistent with where I put the seeds and the plants seem pretty much all of the same type, coming up at the same time.
Alternatively of course, they could be really uniform and well spaced weeds, and IâÂÂm just being ultra-hopeful!

Thank you for your help guys.

Looks weedy, very much like Mercurialis annua, (annual mercury?)

Yes - I'd also say Mercurialis annua, Annual Mercury. Common weed species.

Thanks everyone.

Spot of weeding tonight then!