Germany goes east first in 1914, not doing an offensive campaign in the west, and not violating Belgian and Luxemburg neutrality. Germany is hoping to avoid altogether, and at the very least significantly delay, any British participation in the war against Germany and its ally Austria-Hungary while these two Central Powers absolutely manhandle Serbia and settle the Balkans to their satisfaction and sharply defeat the Russians, at least throwing them out of Poland and Lithuania and buffering Austrian Galicia.
However what I would like to focus on in this thread (...) is British Cabinet and Parliamentary politics about handling the war in Europe, or entering it
If Germany commits to an East First strategy and, as per the OP, wants to avoid or at least delay British entry into the war, then we may safely assume that Germany will refrain from decaring war on France and Belgium on August 3rd. This is what prompted Britain to declare war the next day, after first issuing an ultimatum, and in this case, such declarations of war on Germany's part would obviously be counter-productive (and in fact completely insane).
The fact that Britain issued an ultimatum in OTL is telling. They didn't declare war right away, and didn't even tell Germany not to fight France, but ordered the Germans to back out of Belgium
immediately. Certainly, there were many in British politics who wanted war with Germany; but without a good reason, it would be a damned hard sell. With the invasion of Belgium, Germany handed then the perfect justification.
If Germany goes East First, then the sequence of events is as follows:
First, Russia tells Austria that if it goes to war with Serbia, it'll be at war with Russia as well. This ensures that everybody knows there's going to be a larger war unless Austria backs down. Austria doesn't back down. Austria declares war on Serbia on July 28th, and in doing so, is from that moment on also at war with Russia. On August 1st, Germany declares war on Russia, honouring its alliance with Austria.
And... that's it. France may be assumed to join Russia's side very soon, but the French government was in disarray throughout July, and only declared war on the Central Powers on August 12th. Let's assume it still does so. At this point,
France is escalating a shit-fight in Eastern Europe into a broader conflict. Its reasons for doing so are clear, but not automatically sympathetic to an outside observer. Looking at this, Britain isn't going to be very happy to just jump into the fray. Unlike in OTL, Germany can't be cast as the obvious aggressor. To a lot of people, it'll look like France spoiling for a re-match after the French defeat in the Franco-Prussian War. "Sounds like a French problem to me, mate."
Overall, Britain is going to be more sympathetic to France and Russia, but won't actually join the war over this. It's going to be more wait-and-see. And what is seen, soon enough, is pretty clear: France throwing its soldiers into the meat-grinder in return for little to no gains. That's not an incentive to join. (Meanwhile, France has two options: either try to break through in Elsaß-Lothringen, which is frankly hopeless, or pressure/invade Belgium in the hope that the German forces can be encircled, which is both doubtful and makes future British support far less likely.)
The British position, I'm pretty sure, will be to call for peace negotiations in London. Getting everybody to agree to peace with honour is really the only sensible move here.
Given the circumstances, it may even be possible to make it happen. Simple deal. France gets to keep the Francophone bits of Elsaß-Lothringen, which it has presumably occupied. Germany, having been able to dedicate more troops in the East, will have occupied the Polish heartland, and this is separated from Russia to become an independent country, where Germany can also dump all Polish dissidents from within its own borders. Russia has occupied Galicia-Lodomeria, and keeps it. Serbia gets screwed over, and the Austrians get to exact their vengeance there.
Everybody goes home by Christmas, and Britain never even gets entangled in the war. But nobody gets an overwhelming victory, and the balance of power doesn't change meaningfully. Britain has made no enemies, having actually facilitated a pretty reasonable outcome.
(Now, would everyone be amenable to that outcome? It seems to me that Germany and Austria would be, but Russia and France would object. The result of that is that Germany and Austria can just say "offer's on the table, yours to take". This makes them reasonable, and makes France and Russia the ones perpetuating the war. Which makes British intervention on their side very unlikely...)
In the end, by not fighting, Britain will be the biggest winner of all. And under these circumstances, that'll be far more clear than it was in OTL.
