The same thing happened to me when I grew some wallflowers from seed a few years ago. They flowered really well the second spring, but were huge, rather leggy, plants by that point. I haven't bothered growing them by seed since, as I find the bare rooted plants sold in the autumn work better for me, especially if rotated to a different spot each year.

If growing wallflowers ideally they need to be sown NOW infact ours germinated at work last week. They are in plugs and will be transplanted out into growing on beds before sale in mid to late Autumn. If the plants in their early life suffer a check in growth or were sown to late in the seaon they may well not flower the next spring.
One way around this is to grow the variety AIDA which may well now be called CHARITY this variety will flower from Autumn through into Spring and beyond as it does not need winter to initialise flower.
Hope this helps

Thanks, Plantzzman.
Can't remember exactly how they got treated now, but no doubt they got neglected at some point. Do you think they will ever flower? And is it possible/worthwhile to take cuttings?

I'm not sure but they are planted to flower early or late in the season. Take a look at the shops that sell bedding plants and you will know.

Try cutting them back and waiting another season. They flower six months apart so you might get something out of them.

If you have missed the one you might get the other. I doubt the dry weather has slowed them as they will grow on top of a wall if the infill is lime rich.