There are lots of plants available of 'Pixie' and 'Durham Early'.
Having grown 'Pixie' as a summer cabbage I can recommend it. Nice small heads suitable for all but the largest appetites or families. Plant at 9" (20-25cm).
'Durham Early' is tried and tested and should be planted at 12" (30cm).
Check the tips for planting brassicas in the Hints Archive (Members) and net for pigeons etc.
When harvesting, cut alternate cabbages, leaving those in between to continue growing larger.
If you cut the heart off leaving a ring of good leaves on the stump, cut a cross in the cut end and the buds in the leaf axil will sprout to give Spring Greens. That way the crop will last you for weeks or even months!