In the absence of the Schlieffen Plan, the military forces of the German Empire would shift their main effort from the campaign against France to the campaign against Russia. This would have led to an earlier defeat of the Russian forces invading both Germany and Austria-Hungary, followed by a counterattack into Russian territory. Thus, much of what the Germany of our time line captured in the summer of 1915 (Congress Poland, Lithuania, White Russia, and Courland) would have been taken in the summer and fall of 1914.
In the absence of a hostile British Empire, the naval forces of the German Empire would have been able to shift their main effort to the Baltic. This would have led to the defeat of the Russian Baltic Fleet and the conversion of the Baltic into a German "lake." This, in turn, would have made possible German landings in various places along the Baltic littoral, particularly Finland and the Baltic Islands.
If the events of 1914 failed to convince the Russian Empire to sue for peace, then a second series of offensive actions in the spring of 1915 would have achieved that goal. In particular, we would have seen a powerful German army, supplied largely by sea and cooperating with smaller forces landed at places like Reval and Narva, marching through Livonia and Estonia in the direction of St. Petersburg.
In the West, the absence of a German invasion of France would have denied both French civil society and the French Army the grave threat that, in our time line, caused those entities to overcome the internal problems that had plagued them in the pre-war period. Worse still, the costly attempts to by French forces to break through the defenses of western Germany would have led to indiscipline in the ranks and the sort of high-level campaigns of recrimination for which both the generals and the politicians of the times were famous. Thus, if the French managed to stay in the war until the end of 1914, they would have probably sued for peace sometime in the spring or summer of 1915.
Within the United Kingdom, there would have been a "war party" arguing that, should Germany defeat Russia and France, Germany would dominate the Continent. At the same time, the newspapers would have been full of tales of the atrocities inflicted by Cossacks on the civilians of East Prussia. (The tale of the young woman at the telephone exchange, who was shot by the Russians for the crime of reporting Russian troop movements to German forces, would have resonated deeply with the British public.) Thus, it would have been very hard for British politicians to countenance a "war for the sake of Russia."
In the end, the best that the British government could hope for was an early end to the hostilities, and thus a limit to German conquests in the east. Thus, the British Empire ended up playing the role that the United States had played in the Russo-Japanese War. That is, just as the US wished to end the Russo-Japanese War before Japan acquired too much territory on the mainland of Asia, the British Empire wished to end the War of 1914 before the Germans could acquire too much territory from Russia.