We planted seeds and they grew. All the books say that it is all but impossible to grow these from seed and if you succeed it will be 2 years before a crop appears. We have found this information to be rubbish. I had artichokes in the first year, about 10 from 8 plants.
The books say a light loamy soil...we have a clay based soil but we did add lots of manure before planting. This is perhaps the reason that they are thriving.

Planting time here is January inside and end of February outside. In January we apply a mulch around the base of the plants so that in the summer we can water once a day in the evening. (Although they do get a lot of the washing up water in the Summer too)

Harvesting...cut the heads while they are unopened. Cut with 2 inches of the stem.

Problems
Slugs...we don't have that problem here.
Aphid ... they like the developing flower heads. We found planting garlic with them stops the aphids and prevents the need for sprays.

Plants about 6 weeks after planting out. Thought the spacings were about right. Then I saw a fully grown one in a garden and it was massive.

This is what they are like now! I think they could have had more space between plants but it doesn´t seem to halt their growth.