I know there were several British initiatives to hold peace meetings during July of 1914, one of them was to be in London, but as far as I remember none of them bore fruit. There was much talk among sides prior to hostilities but very little between them. You must remember that at the time "mobilizing" for war was considered about the same as wheeling out the missiles and bombers today and going to Defcon-ll. Once the nations involved started mobilizing things were set in motion that were almost impossible to stop. Most of all given the War fever and Nationalism in Europe at the time. There was a whole lot of 18yo men with nothing to do and major decisions were made by an elite few who all thought the war would be a short affair that would lend glory to their legacies. It was an age of Empire in Europe, Empire and Nationalism. I dont think anyone understood exactly what modern weaponry would mean to the battlefield.
Even if such a meeting happened I dont think it would have done any good. The Kings of Europe wanted a war and they convinced the people it would all be a glorious adventure.