How do you spell this: Tsudoku Sudoku?

I just got home from a three day trip in the mountains of West Norway.
More about that tomorrow, I reckon.

On the trip home, though, I was caught by the Tsudoku-germ that has raged Norway the last couple of weeks. I was sitting there on the train for six hours on the same puzzle. I think I’ve met the wall. Which is why I’ve uploaded the board here:

Any help appreciated. This is the original board. And this is what I’ve got so far.

EDIT 10th of August:
For those of you still scratching your head: here’s the solution!