Aye, the potted one does look about to flower and it has for about 6 weeks
They are both driving me mad, I planted a load of different fruit and veg seeds in pots last year from melon seeds to pepper seeds and would love to know if it's one those or if it's just some mad weed I haven't seen before.
It'll certainly teach me to label my pots
I have quite a few flowering and pretty "weeds" that I let grow wild in parts of my side yard. Anything with abundant seed heads, flowers, or just interesting foliage - for the pollinators, the birds and because I think they're pretty.

And as anyone seeing my yard would attest, I don't go for the carefully manicured look! I like that there's an abundance of native flora around me. The guy who mows my property grumbles a bit because I put little markers next to the things I want him to mow around. The back part of the side yard is a tangle of blackberry and raspberry bushes, giant burdock, phlox, datura, some wild orchids and other things I have yet to identify. And along one side there are masses of small wood lilies.
I've found this site very useful in indentifying native plants:
https://uswildflowers.com/wfquery.php?State=MI
Maybe you can find something similar for your area of the UK?