To address the follow-up question, it is true that some of the occupation policies of Germany in central and eastern Europe during WWI foreshadowed some of the mentalities of the Nazis in WWII. But remember that Hitler and the Nazis dictated civil/military policy in the East in WWII - not the conservative military establishment, or even Hindenburg or Ludendorff (both significant in the eastern front in WWI as well as the story of Hitler's rise to power, but deceased by 1939). If you are interested in a fascinating read on this subject, check out the work of Vejas Liulivicius (U of Tennessee).

Remember that while the wars were inexorably connected to one another, they were fought with an entirely different spirit and to different ends. WWII was fought (on Germany's side) to build a great 'Third Reich.' WWI was fought out of fear for their neighbors growing in power. Much different. That's not to say they didn't have some idea of what they wanted to do after the war, but it was not, unlike WWII, waged initially to establish a great German empire. It was about continental dominance and shifting the balance of power. And remember that, even though Germany bears the brunt of blame for WWI, they didn't mastermind it nearly to the extent as in WWII. Starting that war was much more of a team effort, relatively speaking.

Now, to the question at hand: what would the Germans have done with the UK in WWII? On the Nazi hierarchy of 'ethnicities' (let's just imagine scare quotes around any Nazi idea I mention, shall we), the French were somewhat close to the top, and the British even higher. Hitler's main beef with them was that, apart from being enemies of the Reich, they were a 'nation of shopkeepers.' He disliked Neville Chamberlain, but had respect for the nation as a whole - compared to the Slavs and Jews, that is.

If you're asking whether genocide was 'planned' for the UK - we'll never know. Not in the short term, by any means. This is when someone inevitably points to a document, and says 'aha!' and thinks they've found the smoking gun. It doesn't work like that. Hitler made many, many plans, not all of which came to fruition. Just because he may have wanted to do something, that doesn't mean the time would come when it could become a reality. I mean look at France during the war - the Nazis had roadblocks galore even exterminating the French Jews, much less other French folk. And there just weren't enough Germans to do the work without local help, for France or the UK.

This brings us back to the near occupation of the UK. Always keep in the back of your mind that the Nazis could never have maintained a true police state over the continent of Europe without help. This was true in every single occupied state, except for Germany itself. You would have had a British puppet government made up of willing collaborators acting out of racism and opportunism, like in France. Churchill and de Gaulle would have eloped to some distant land, maybe the US, and discussed battle plans (a little tongue in cheek, but not far from the truth probably). What you see with Vichy France is that French politicians believed that if they were helpful enough to the Germans, they would have a near partnership after the war, while recognizing that they would always be answering to the Reich. Still better than Poland's lot, right? Britain would have been a vital component of the Atlantic defense against the US. Hitler knew he would eventually have to face the US, but hoped to put it off until Europe was conquered. So, in that sense, Britain would have been an important satellite nation to keep reasonably happy - only until the world was conquered.

As for the UK's empire, Germany obviously would have taken their spot as commander in chief. The military and economic potential of the major colonies would have gone to serve the Reich. Let's not open the can of worms of what would happen when you get new colonial rulers rather than the Brits - with whom the Indians, etc. had come to build relationships after hundreds of years.

So, after all this ideological background, German 'plans' for the UK involved the seizure of the administrative sections of the country for occupation after Operation Sea Lion (the invasion). Some sympathetic local authorities probably would have been propped up, accompanied by a few German watchdogs. Maybe eventually the UK would achieve a Sweden-like independence, where they could govern themselves, but only if they supported Germany in any way it asked. But remember that the Nazis were only good at war planning. Their whole ideology centered on a 'frontier mentality' - meaning that they saw the ideal German as one whose spirit was molded by fighting abroad in the mud (the men, that is). That required, basically, never ending war. As history proved, Germans, as a relatively small nation, were not capable of occupying an entire continent, much less doing that and fighting overseas.

Just to clarify, do you mean if Britain signs a peace treaty or if Germany successfully invaded and occupied the UK?

Follow up question, what were the plans for France and England had Germany won WW1?