Hard to tell from this altitude and the lens Vaseline factor. Are those tiny yellow flowers? If so I would suggest it might be horse herb. That can be tough to get rid of or easy depending on your lawn type. Where do you live? What kind of grass do you have? Can you be more specific about the brand and name of the 2-4,d product you used? They're not all the same. Furthermore if you have St Augustine, you may have killed the grass with that spray.

Looks like POA, spray some Tenacity on it and they will all bleach

Narrow leaf plantain, Plantago lanceolata.

Parietaria hespera? The leaf surfaces should be glandular and the leaves should have hairs around their edges(ciliate on the margin). They don't show up in the photo, but the succulent stems do. There's a lot of leaf variation in this species. Some individual plants have leaves that are acuminate, and some can be very oval,round shaped, but your plants have the more standard shaped leaves. If that's what they really are? Lol. I see that Pellitory of the Wall, P. juidaca is invasive in quite a few states over here, fortunately not mine. Doesn't everything imaginable grow on walls in England floral? You could get a lot more vegies by growing them on your walls.😂 I did envy your misty climate when I struggled with growing butterfy bushes. I would see photos of 16ft tall, lush bushes in England, and there would also be pictures of butterfly bushes growing in walls.🤣 I realized butterfly bushes aren't worth the trouble, but if I lived in a warmer climate I would possibly grow unique species of Buddleja. Is Buddleja invasive in England?