This question is focussing on the period between 1700 and 1900 (the year when Europe was at its most powerful).
When recounting famous historical political figures, UK ones are slim at best and none at worst. Famous UK military figures like Wellington and Nelson are well known, they weren’t political (Wellington did become PM but his premiership wasn’t that well received).
In comparison, other major powers like Germany and France have Bismarck and Napoleon and Russia had Catherine the Great.
Why did Britain (who had a comparative influence on world events - if not more - not produce those famous leaders during these times?)
I must strongly disagree with your premise. Please don't take this the wrong way, but questions which hinge on "Why do I not know about X" often speak more to the education of the person asking it than the situation about which they ask. I don't mean that to come off snidely, rather I just mean that, for whatever reason, it seems like your history classes didn't focus much on British political history, so you never heard about figures like Disraeli, Pitt, Pitt, Palmerston, Walpole, Peel, Lord North, or Gladstone. Even if we don't want to count about stuffy ol'Prime Ministers, what about Queen Victoria, the British ruler for more than half a century who gave her name to the common term used for the late 19th century in the Anglo-American world?
I also have to take issue with your casual dismissal of figures like Wellington and Nelson (which by extension also invalidate Churchill, John, not Winston). You are willing to consider Napoleon, whose claim to "great leader" status is most certainly contingent on his battlefield accomplishments (Ask someone to name what he is famous for, and they'll probably cite a battle, not some political reform he brought about), yet dismiss the man who played an outsize role in finally bringing Bonaparte to his knees. Likewise Bismarck might not have been a battlefield commander, but the Iron Chancellor's 'realpolitik' took Clausewitz's dictum that "war is politics by other means" to heart more than once.
Anyways though, the root of the issue is that, all you've done is named one German, one Russian, and one Frenchman, and I think Victoria, at least, is equal in fame to them, and I would venture a head higher than at least Bismarck and Catherine for the common "man on the street". Name me a half-dozen famous German leaders from 1700-1900, tell me of several Czars who everyone knows about from back then (I'll spot you Peter the Great, but let's be honest, Alexander II probably should be number three, and 9/10 people won't be able to tell you who freed the Russian serfs), and you might strengthen your argument, but Victoria alone would seem to undercut the premise here.