This is a foxglove called 'Primrose Carousel', named because the flowers grow all round the stem. I prefer the traditional 'all the flowers on one side' type but this is such a pretty colour. Thompson & Morgan started selling seed of it a few years ago, very expensively, and it was a big success. I grew some plants, was pleased with them and carefully saved seed to sow again. I have other foxgloves in the garden and none of the new plants I raised came true. Every now and then though, one pops up, as seen above. Here's some more
I'm pretty sure this is a poppy called Chelidonium majus. This has appeared with the builders' weeds which is rather sickening as I once grew it deliberately from Hardy Plant Society seed.
Another happy self-seeder: Verbascum nigrum. I think it's a biennial and once you've got it you'll never lose it. Rather early for it to be in flower but this is one of last year's flowerers which I neglected, so it's behaving like a perennial.
An old cottage garden favourite, Sisyrinchium striatum. Tough as old boots and very keen on seeding. There is a pretty variegated form called 'Aunt May' which I used to have but like many selected forms it's not as perennial as the original.
The pretty Welsh poppy, Meconopsis cambrica. This plant is virtually growing in concrete but I'm pleased to see it anywhere at this time of year.
The moral of this post is: don't weed too enthusiastically.