I've always wondered about this. While all of Europe was at one time or another at war with Napoléon the only power to remain continuously at war was the United Kingdom. After the breakdown of the Treaty of Ameins there was not another peace treaty until Fontainebleau in 1814. So what made England, alone among all powers, unwilling to make even a short peace with the French conqueror? Pride? The fact that both nations were basically at a standstill? Or another reason I haven't thought of?
Reason:
1 - Making peace with Napoleon would be the same has admitting that they can't defeat him;
2 - The UK had bet to much money on this war;
3 - If they made peace they would allow France to create a powerful navy, that could be used in an invasion;
4 - They didn't trust Napoleon to keep his word;
5 - Their European policy was to stop a country to dominate the continent;
6 - The desire to capture more colonies, if they are at war with France the Netherlands and Spain are also at war with the UK, so the RN can steal their colonies;
7 - Isolation, the UK had been isolated from Europa for a long time, the only reason the rest of the continent didn't join France in a war against the UK was because they were more afraid of France, a close neighbor, than the UK, a far away neighbor;
8 - The continental system;
9 - The Sicilian question. Unlike what you may think the UK and France made several peace talks. In exchange for confirming the continental conquests, the UK got to stay with the colonies that conquered. The main problem was Sicily and Hanover, France wanted Sicily in exchange for the restoration of Hanover;
10 - For the majority of the war period the British Army (BA) waged low-intensity warfare, so their wasn't big manpower losses that forced a peace treaty. In the peninsula war, it were the guerrillas that killed the majority of the french casualties. Only in Waterloo and in the latter stages of the peninsular war that the BA played a central role;
I think these are the most important reasons.