Tell me about growing cabbages and their relations

Look see I'm failing. My calabrese grew little heads last season and went to flower in 24 hours. My purple sprouting broccoli managed to get two plants with purple sprouts on. My January Kings were small! My spring cabbage (what survived the butterflies) is small and has tiny hearts.

The sum total of my knowledge is to plant them out in firm ground that has been composted but not manured and to water when the weather is dry.

No I do not have club root on the plot; yes I have composted the soil every season. It's a sunny site but the last two summers it hasn't drained well because of the rain and it's clay. Every one else can grow decent cabbages but me.

So let's start from the beginning. The calabrese and purple sprouting broccoli were sown straight into the ground and thinned out when big enough to handle. The cabbages were bought in. The person who bought me the spring cabbages has ones twice the size from the same batch of plants.  And he put manure in his soil before planting which I thought was norty.

So teach me about the cabbage family please.

Manure is fine for brassicas, in fact it is recommended, in the preceeding Autumn, they also need an alkaline soil so lime may be needed a couple of weeks before sowing.  You can't manure and lime at the same time as they react apparently 

Not that I'm an expert, this is my first attempt this year, but I do have John's book to hand 

18" for things like cabbage, (cabbage mostly  ), 2' for sprouts & 2'6" at least for sprouting brocolli.

Enough for cabbages which still had small heads (any suggestions as to why?), not enough for purple sprouting broccoli (would this explain why one plant had heads and the one next to it not?) it would seem and possibly not enough for calabrese which went to flower almost instantly (suggestions please as to why).

How do you get round the very firm ground needed vs. raised "no dig" beds please for the brassicas?   Just finished my 100' x 4' longest raised bed(!!) but plan to put the brassicas in an undug other area for that reason... if it is possible to put them in the raised beds it would be good 'cos I got plenty of room 

Off to put my spuds in ....

These are my Hispi cabbages in a raised bed.  It's also not a very deep one so results will be even better when it is.  They are 12" apart and hearting up nicely.  My new ones are going in at 9" apart, maybe less so I can harvest every other one first and let the rest heart up more.