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I've camped in half the counties in England. Genuinely nobody gives a toss. I've only been "caught" twice out of literally hundreds of times, and both times all I got was a 'good morning!'. And it's de-facto allowed on long-distance trails like the Ridgeway and Pennines (source: certain council websites, and a personal experience I had with the police near the Ridgeway who thought it was cool that I was camping).
Just don't light fires unless there's zero chance of getting caught, and keep in mind the first rule of stealth camping: no matter how early you wake up, there's a local dog walker who wakes up earlier.