Thanks bill, I think I understand now. I only have one question. In both of the examples where white plays first there are two outcomes, white keeps sente and the count is unchanged or black is slightly down and gains sente. My question is, if you account for sente in the value of whites last move is the theoretical count unchanged but white at an advantage by playing the last move on the board?

Using the method of multiples for gote (where all the followers are also gote) you can always find some number of multiples such that they are strict miai, and it does not matter who goes first, the resulting score is the same. Dividing the result by the number of multiples gives you the count.

But with sente or ambiguous positions the result will depend upon who goes first. As the number of multiples increases, the average of the two results will tend to the theoretical count.

In the SGF files some of the variations are mistakes. When White plays first and Black replies correctly in the S example, Black always gets an average of 12 points. When White plays first in the Q example, with correct play Black always gets an average of 9 - 1/N, where N is the number of multiples.

See http://senseis.xmp.net/?MethodOfMultiples .

I'm still not totally confident I can find the value of moves properly so I'll try and get my head around that more before I dig into the nitty gritty bits.