Hello Alan, yes you could plant it after clearing tomatoes in the greenhouse. But it will make less dense hearts in the spring, briefly, before sending up a flower stalk in late April/early May. And yes the outer leaves are bitter but alright if diluted with other leaves.
In view of the warm weather you could still sow rocket and mizuna to plant by month’s end. I sowed two or three weeks ago and wish I had waited another week as growth has been so rapid. It means here that we will have a surplus of leaves in November as outdoor endive, radicchios and orientals are still cropping. Nice problem though.