Thanks Aunt Sally,
I checked out the link you gave me. My goodness they do grow tall. I'm assuming the greenhouse in the pic is a standard garden one and about 2.5m tall at the roof apex.
I think I'll leave them out of the rotation and give them their own bit of ground. I have a spare bit in the front yard. If nothing else it will give the people walking past something to look at.
I have now read a few other articles about Jerusalem artichokes, mainly how to cook with them, and I love their alternate name of fartychokes, not sure how I will deal with the effects but nothing ventured as they say and apparently some people never have a problem. One article said to eat small quantities at first and build up. LOL I just love growing new things. Last year it was Horseradish.