It does indeed appear to be Fomes Fomentarius, alot of people believe that it only grows in the north on dead birch....however it is actually fairly widespread and in the south, tends to grow on beech and only occasionally on birch.
I am not an expert on fungi, but what you have there is very similar to FF that I have found but a slightly lighter colour.
One test which sometimes works......the white pore mouths on the bottom of the fungi will, if its alive, turn a pale purple when touched.(has only rarly worked for me.)