Installed the MSDN ISO. Went without a hitch. Accepted the KEY and is activated.
I have just finished customising and so far have not encountered any problems.
Just been looking at the threads regarding the automatic upgrade-YEK.
I upgraded my 8.1 install using the ISO, now it does not want to activate says it is invalid, both the key that it placed in there itself (I assume a 10 key ?) and my win8.1 key. Does not accept either..