Hi Martin,
I wonder how you got on with your Sonchus acaulis?
I tried to grow some from seed last year. They germinated erratically (the few that did) but did not survive very long. I have some more this year. I sowed some in the autumn and a few last week. No sign of life from either batches yet.
What on earth I am going to do with such plants on a small and already cluttered balcony, I have no idea. I will cross that bridge when, if ever, I come to it!