I grow Greyhounds every year and if I didn't know better I would say they look as if they are ready to bolt but Greyhound are really good at not bolting. As every one is affected it's probably not the odd insect in the soil either (I'm assuming you have a good row of them). Another reason may be a deficiency in the soil. Do you lime your soil? Apart from that I've never seen my cabbages like yours - perhaps it's the weather. I've had rain and cold but not as much as UK and it is warm in between. Mind you, my veggie plot is way behind this year.
It is a bit too late to sow again but you may find some plants in a nursery or someone may have a few left you could have. You could sow some seed and with fine weather be able to have some "greens" later on but that's probably about it.
If they were my cabbages I would dig them up and harvest what I could from them, slice, blanch and freeze and not grow cabbage in that soil for the next couple of years. By the look of the heart they are not going to get any better and you may end up with nothing.
It's such a shame when things go wrong. All that hard work for zilch.