Thanks to you both. I'm looking forward to seeing what happens next.

Thanks Dave
I hope I didn't harm it too much by failing to provide soil. I hope it's the Angle Shades moth - it's beautiful. Fingers crossed that whatever it is, it's still healthy.
Thanks for the ID of the others - I'll know now to place twigs and not soil in their container

These are the other caterpillars. Are they the same?

This is the fella - it didn't turn brown at all. ???
His eyes became a metallic brown colour a few days before he pupated, but that was all.

Thanks Misha. Blimey, I hadn't even thought of that. Will it be ok do you think? I just assumed it was a large or small white because it was eating cabbage and that it wouid pupate above ground. Should I put a layer of soil over it? Will the others that I have want to bury themselves too?

I was given some cabbage and kale a while ago upon which I found some eggs. They successfully hatched a week ago and are now doing very well. There was also a large caterpillar which I've housed in a small aquarium with food and paper towels. It was doing well for a week or so eating good amounts of...

Thanks Trev,
I didn't know to count the legs
I've googled it and found it to be an Alder sawfly, which is actually a bit disappointing. At least I can put a name to it now - thanks.
Alison

I'm desperate to know what caterpillar this is - any ideas?

Thanks