I think this is far too long Christian. I bought a piece of 20mm granite
2m x
300mm for the shelf over the concealed cistern in my Bathroom.

Well, I've redone it by inserting a couple of column pillars which I had
bought with the kitchen that I had lying around. So I now have:

++----+----++----+---+----+---+---+
|| WM | TD || DW | +----+ | |
|| | || | 1 |SINK| 2 | 3 |
++----+----++----+---+ +---+---+

Support profile:
^^ 1.2m ^^ ^ ^ ^ ^ ^

The 1.2m section is back supported and may have a little support from the
appliances below. The granite is 30mm thick, rather than 20mm, so should be
a little stronger.

Christian.

P.S. I'm DEFINITELY getting them to template, deliver and install.