Still irrelevant, unless you intend to argue that for instance China and India were the two main world powers of the 20th century.
From a military point of view, the UK was the main naval power with, at its apex in 1850 twice as many guns as its closest rivals, France and Russia. However, its army was dwarfed by those of continental powers. So, it wasn’t a dominant military power.
Economically, the GDP of the UK in 1870 is estimated at about 100 billions equivalent 1990 dollars, barely above that of the USA (98 billions) and 30% higher than that of France and Germany (72 billions).
This doesn’t make the 19th century UK the dominant world power by a large margin. It makes it a country somewhat wealthier than its rivals.