Britain could no more refuse to fight the Great War than she could the Second World War. It was fight or die.
We can rarely be absolutely certain what was in the hearts and minds of the participants. They have left papers, memoirs and diaries to be sure, but all of us tend to see and record our own actions in the best light possible and those of our enemy in the worst. Almost every book on the Great War I have read brings up the issue of the differing accounts (concerning the same events) left behind by participants regarding who said/did what and when. etc.
The fact is that all the belligerents had the choice of fighting or remaining neutral. Certainly neutrality had its own set of risks and rewards. The US certainly didn't suffer from its cynical policy of sham neutrality and a very late tossing of its hat into the Allied ring. It may also be cynical to say that treaties often ARE 'scraps of paper', but ignoring inconvienent or ill concieved treaty agreements is often regarded as an expidient of national survival. Whatever their motivations, greed, honor, fear, revenge, IMHO, the belligerents did what they felt best satisfied their particular goals. If Britain felt compelled to go to war in 1914 it was her decision. I feel it was the wrong decision for both Britain AND the rest of the world, for whatever else can be said about Britain she was on the whole a tremendous force for the betterment and advancement of all mankind. To have lost that influence has made the world a poorer place. And IMHO it was unnecessary. The diplomatic skills Britain had perfected over hundreds of years should have seen her through all the stated motivations for war (defending poor little Belgium, defending the status quo, helping France, etc) without the need to turn the European War into the first world war. All motivations save one. I am left with only two answers to this riddle. Either Britain horribly miscalculated the downside or was driven by inviolate notions of honor which we haven't seen the likes of in a very long time. Given that Albion had successfully manouvered her way thru hundreds of years filled with crisis, I am compelled to conclude it must have been the latter. Whether this is enough consolation for the losses she suffered only they can say.
Regarding WW2. While horrifying and terrible, what a joy it would be for all of us living today to have an issue before us of such clarity as the need to defeat Hiltler. While we might debate that Hitler could possibly have been contained earlier, the fact that Britain alone held out against Nazism, will always be a source of pride for Britain, and a cause for respect from the free world.