So why would the United Kingdom not enter the war? It's not in their interest that a single country achieve hegemony over europe. And Germany having control of the Belgian ports was innaceptable. If you want a neutral United Kingdom in that war you must change the POD.
One possibility is the scenario I made up in the other "WI Entente is the aggressor" thread:
PoD 1: a freak accident claims the life of Von Schliffen. In the reshuffle of the German High Command that ensues, a hard look is given into his (in)famous plan, and the conclusion is that it is too diplomatically risky and logistically difficult to implement. The High Command notifies the Kaiser that Russia First is the best option in case of a general European war. Since the East strategy promises a somewhat longer war than the defunct Schliffen Plan, the German government takes steps to secure the friendship of other European powers besides Austria in case of a general war.
It cultivates the support of Turkey by giving some military and economic support to the Ottoman Empire and this hence strengthens the hand of the Germanophile faction in Constantinople. It pressures Austria to comply with its treaty obligations towards Italy about compensations for the annexation of Bosnia. Vienna drags its feet, but eventually Italy gets guarantees to receive Trento and Gorizia, and its irredentist claims on France, in case of a general war, so Rome tears up the secret neutrality treaty with France. Berlin also makes some openings to Britain about a reconciliation and solution of the naval dispute, but the talks fail to achieve a major breakthrough since Germany is unwilling to give up too many of its naval toys. The talks generate a little more goodwill for Germany in Britain, however.
PoD 2: In Spring 1914, Tsar Nichy has a dream which he interprets as a clear divine mandate to be the gallant protector of Slav peoples. He gives a more aggressive Pan-Slav spin to the Russian diplomacy in the following months.
Come the Franz Ferdinard assassination. Emboldened by Russian support, Serbia flatly refuses Austria any real cooperation about the investigation of the assassination and curbing the activities of Pan-Slav terrorist organizations. Austria declares war. The actions of Austria and Serbia are controversial in European countries, but many are willing to give Austria the benefit of the doubt about its denunciation of Serbia as a terrorist haven.
Seeing this as a clue from Heaven, Tsar Nichy pushes his goverment to mobilize, and when Austria refuses to back down, Russia declares war to Austria. Germany declares war to Russia. France declares war to Germany. Italy, feeling bound by the terms of the defensive alliance, and clutching the guarantees about territorial compensations for its efforts, declares war to France.
Since Russia is going in a belligerant mood at the moment, nobody in St. Petersburg cares fast enough about the actions of the rogue commander of the Baltic Fleet, who has decided that Sweden is going to join the CP and a pre-emptive attack is warranted, so he goes and shells the Swedish fleet. Outraged Sweden declares war to Russia that solidifies its reputation as an aggressor. In the face of recent Russian actions and the array of forces already raised against the Entente, the Germanophile faction in the Ottoman government, which argues this is a unique opportunity to cut down Turkey's traditional enemy, gets the upper hand and the Ottoman Empire declares war to Russia.
In Britain, the majority opinion holds that a war which Serbia, Russia, and France brought upon themselves against most of Europe is no matter to expend British blood and money on their behalf and the anti-German faction is shouted down. Britain declares its neutrality. Soon afterwards, the Home Rule goes into force and Ireland explodes as Ulster Unionists take arms to oppose it, taking Britain's mind away from continental issues.
America clings to neutrality, but majority opinion largely favors the CP, as Americans of German, Italian, and Swedish descent lobby for them.
Bulgaria joins the war and Serbia is overrun and its army encircled and destroyed by Ausirian, Bulgarian, and Italian (through Albania) offensives. Greece switches to pro-CP neutrality. Romania, seeing that the Balkans have become a CP playground, decides that a safer Bessarabia consolation prize is better than a risky Transylvania top prize and joins the CP.
Russia is gradually worn down as the bulk of CP forces are thrown against it from Finland to the Caucasus. French offensives in Alsace and the Alps get a bloody nose against German and Italian defenses. The harried Entente makes tentative peace openings but talks break down as France and Russia are unwilling to pay the price that the CP ask. Dissent grows in Russia until at the beginnig of 1916, it explodes in revolution. The Tsar is toppled and Russia descends into chaos as various factions, included the Communists lead by Trotzki (Lenin is fuming trapped in neutral Switzerland since the CP don't see necessary to give him free passage).
Russia signs a peace treaty, which sets up Finland, the United Baltic Duchy, and Poland (with the Second Partition border) as independent CP satellites and gives Bessarabia to Romania and Transcaucasia to Turkey.
The full might of the CP is hence thrown against France and French defenses are broken through sheer force of numbers. Paris, Lyon, and Marseilles are occupied and France surrenders. In the peace treaty, Germany annexes Lorraine, French Morocco, Ubangi-Shari, Middle Congo, Gabon, French Dahomey, and Ivory Coast. Italy annexes Nice, Savoy, Corsica, the Riviera, Tunisia, Chad, French Somaliland, Senegal, and French Guinea, as well as Trento and Gorizia. Austria annexes Serbia. Bulgaria annexes Vardar Macedonia.
France descends into chaos but CP military intervention crushes Communist insurrection. It's a coin's toss whether the CP intervene in the Russian Civil War to suppress the Reds. If they do, it is fairly likely that after some further convulsions, Russia descends into fascism. If they don't, most likely we get a Trotzkist Soviet Union. France is fairly likely to slide into fascism, but it is anyone's guess whether they are going to have another turn at revanchism after getting beaten twice in two generations (and thrice in a century). Britain wrings its hands for a while about CP hegemony on the continent, but eventually they realize that it's not the devil and they can mkae nice business with it, and relations between the British Empire and CP Europe improve from that point.
Germany and Italy have some political convulsions as the masses claim their due for the war, but eventually they get headed towards a largely stable liberal consitutional monarchy, just like Sweden. It's everyone's guess whether victory breathes new life in the Habsburg empire and it evolves towards a stable Quadruple Monarchy. Alternatively, attempts to reform fail, internal instability resurfaces, Germany tires out of bailing out the Habsburg, and in the 1920s it collapses and is partitioned by Germany (Austria and an autonomous Bohemia-Moravia), Italy (Istria and central Dalmatia), Poland (Galicia), Hungary (with Slovakia, Backa, and northern Transylvania), Romania (southern Transylvania), Croatia (with Syrmia and the 1939 Banovina of Croatia borders, minus central Dalmatia), and Serbia (with most of Bosnia). The Ottoman Empire most likely enjoys a rejuvenation.
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