In the late 1800s, there was a pretty good census of land holdings that connected county level records to give national totals for the UK. Land was accounted for on a county by county basis and then organized at the Kingdom level so never officially totaled up across England, Scotland, Wales and Ireland. If you counted up the percentage of the population that owned 70% of all land in the UK, that percentage of of the population owned only 13% of the land in Russia. Even in Prussia, as distinct from Germany in general, the percentage was under 30%, which about what it was for Austria. The only places where you can even get to 50% is in far East Prussia, the ducal remnant of the Teutonic Monastic State, and one region of Hungary.
Might the absence of a service nobility and primogeniture's non-division of land holdings produce an elite too small to actually run the country? The aristocracy was much larger everywhere else and titles of nobility were handed out right and left on the Continent. Think of all of the von's and zu's in Germany and the de's in France. There were never many more than about 800 title holding aristocrats in the UK. And they were much wealthier than their French, German or Russian equivalents.
Since all of those second sons needed things to do, the various social institutions had to provide positions invested with respectability that were free of aristocratic place holders. In Russia or Austria or France, the institutions would have been filled up with the multi-generational service nobility. In the UK, the aristocracy was simply always too small to actually run the country. They did not even produce enough extra sons to run the place.
Plus if there is no land, enterprising people would be forced into the cities and into trade. A Physiocrat or agrarian song of the soil attitude would just not have the same appeal.
Random fact, the Duke of Sutherland owned roughly 3% of the UK in the lead up to WWI. He owned about 30% more acres than the Klebergs owned in Texas, which is three times as big.