Have you been dreaming about visiting this place, or are you planning to be in London anyway?
Trent Park is genuinely a unique place, not just a museum, but a whole mansion with history. The atmosphere of wartime is recreated there - when the British set up hidden microphones in the rooms where captured German officers were held. They thought they were simply in a relatively comfortable place, but actually every conversation was being recorded. The exhibits tell the story of this secret operation, show genuine documents, photos of the generals who were held there, and explain how their conversations actually helped the Allies' strategy. The atmosphere is quite interesting, especially when you realize you're standing in the same rooms where these secret conversations took place.
Practically speaking: the museum doesn't open every day, just a few days a week, so before you go definitely check the website or call to confirm the current opening hours. It's better to book tickets in advance if you can. I'd recommend taking a guided tour - the guide will tell you details you wouldn't notice just walking around on your own.