Cabbages gone, caulis next?

Hello, I've just torn out the stems of my cabbages in disgust. What I thought was slug damage (beer traps put in last week) has been caused by the tiny pupae of what I believe will become cabbage white butterflies.

The cauliflowers next to them are just coming through ... and they already have tiny eggs beneath the leaves.

Next year I'll get some old net curtain over them early on, but do I try to save the little caulis or do I plant some more seed and make sure the new plants are protected?

Also, are there any environmentally friendly sprays that anyone can recommend?

 

You should be able to just rub off any eggs you see with your thumb and look for the green caterpillars if there are any about. I squish them between the leaf and a finger. Could be something has been along and eaten the eggs for you if you are lucky. I wouldn't be thinking of abandoning them just yet. The plants are looking quite healthy.
The marks in the leaves look like where the eggs were attached. They have to eat quite a bit of leaf as caterpillars before they pupate and the leaves don't look eaten just yet.

 

Yeah just squash them, but look every day, I find cabbage whites usually lay their eggs on the underside of the leaves.