Fixed-term Parliaments Bill

In the scenario that my noble friend Lord Grocott was suggesting, would it actually be necessary under the Bill for there to be a vote of confidence? If the Liberal Democrats had simply decided that they did not wish to carry on in coalition with the Conservatives and made overtures to the Labour Party, there would not have been a vote of no confidence. There would simply have been a realignment within the House of Commons. As far as I can see, the provisions of the Bill are not activated in that situation.