Dual season brassicas

I've been playing with my brassica seed collection today. The aim was to put the packets in sowing date order so that I'd have a packet ready to sow every Leaves Week. 
Sounds easy, doesn't it. However, it was noticeable that some seed companies have different dates for sowing the same seeds. Who do I trust?

Secondly, I found several varieties of cabbage that have 2, widely different sowing dates - some in spring and again later in the year when they would overwinter ready for spring harvest. 
This, struck me as a bonus - buy one packet but sow it twice during the year.
 
Cauliflower "All Year Round" is well known. I've copied this from Kings Seeds :-

Sow October in a cold frame, plant out in March, cut in June. Sow February to April, cut late June to September.

Cauliflower, not being one of the easiest of vegetables to grow is certainly regarded by many old hands as the test of a real gardener. But with good planning, regular care and a small dose of common sense, you can pretty much have cauliflower on the table all year round.

I'll be back later with the dual season cabbages.

I used to grow Sweetheart cabbages which were an F1 variety so very expensive seed! To offset the cost and prolong the growing season making the seed cost more acceptable, I would cut a cross in the remaining stem wjen harvesting.
If I opened up the 'cross' a little bit with a knife I would invariably get new shoots forming on stem which would eventually give me a host of sweetheat cabbage later in the season.
Another trick I have with spring cabbage is to plant them fairly close together and use the thinnnings as Spring Greens allowing the others to heart up later in the season. One year I grew some sping cabbage in the greenhouse in pots which wee sown the same time as the outdoor SC. This also gave me an extended crop.

I have managed to keep Austurian tree cabbage, which isnt a perennial, growing for four years by pegging down some of its branches to the soil (layering) where it has re-rooted!