Genghis, can you tell me where to find your diagram?
I would guess that the .333 diagram is just a copy from the FAA book, and does not relate exactly to the JAA text which specifies Va in words.
Geddifroggy, according to all the feedback we have the JAA examiners think that Va is Vs1g times the square root of the clean config limiting positive g, and that's it. No question that I have seen goes beyond that.I have seen nothing on application of the standard gust speeds,as in Genghis' posted diagram, but there is a specific JAA "standard gust" that varies with height. I have forgotten what it is, but again, this has never been questioned.
Let's not go too deeply into this, the JAR certification rules are a minefield, and pilots do not need to know 99% of them.
Dick W