In many ways, this seems to be true, based on Germany's military power in the early 20th century and economic power today, but what about Germany supposedly gives them such inherent advantages? Is it their geopolitical positioning? Their natural resources? Something else?
I don't believe it's possible for the British to have had a foreign policy that lasted unchanged for a hundred years.
The focus was on what the British believed preserved the balance of power in Europe. Effectively this meant keeping French military ambitions for the continent in check during the 19th century. However this policy gradually began to spread to Russia, which the British believed to be the main threat to the balance, which precipitated the Crimean War.
I believe the British, who had good historical ties with Prussia, wanted to see a larger and prosperous state develop, they were just taken by surprise how quickly this happened, essentially because of Bismarcks maneuvering. A strong German state could push back against Russia and would be a useful continental ally against the French, as Austria ailed during the 19th century and became much less coherent as a Great Power after the comprise of 1867.
The British probably assumed also the challenge of governing a large, locally diverse, German state would take decades to get right, instead through a fairly rapid series of reforms Germany started top outdo her neighbours in production, business, and military development, so that by the 1890s there was a dominant Prussian ruling culture but a federated state system, which had massively benefited from the removal of the old customs barriers. By the early 1900s, the British Liberal party were campaigning for the sort of strong welfare protections that had been enacted by Bismarck 20 years previously (part of his plan to buy off the German working class by giving them a version of socialism still firmly in establishment control). The British had realised at this point Germany was outstripping them not just in coal and steel production, but also in some areas of political development - all in a much shorter time than they had expected. So I think you can say that British balance of power objectives, especially towards the later nineteenth century, focused too heavily on the threat from a contemporary Russia nobody really knew had very deep problematic societal divisions, and developed a blind spot that allowed Bismarck to weld a Germany everyone assumed had irreconcilable differences, into a united and dangerous state.