Well, the problem is, there's no way to enforce what you can call "gentle parenting". It's not trademarked or copyrighted, and there's no Pope of Gentle Parenting that can excommunicate people who are doing it wrong.
I call my parenting gentle-ish. Here's what that means to me (note: I am American, so parenting norms may be a little different here than in the UK). My kids are 5 and 2.5:
-No physical punishment. I'd be OK with slapping a kid's hand away from a hot pan, but not with smacking them afterward for trying to touch the pan.
-No physical violence from kids tolerated. That gets an immediate time-out with no warnings. Pretend violence is OK, though.
-Punishments are time-outs, losing privileges such as watching shows, or logical consequences. Time-outs are one minute per year of age, and no one can talk to you while you're in time-out.
-No humiliation as punishment.
-No destruction of property as punishment (though toys can be taken away for the rest of the day).
-Deliberately destroying toys, whether they're your own or someone else's, is against the rules (obvious exception here for toys that are intended to only be used once).
-I try not to yell, except in emergencies. I will not claim that I always manage to do this.
-No insults, sarcasm, or snark. This one is hard for me, because snark is how I deal with life. Kids aren't allowed to insult people, either.
-Lots of "How would you feel if he did that to you?" or "How do you think she felt when you did that?" questions. I try to teach empathy.
-I'm trying to teach consent. They're not allowed to keep doing something to someone else if that person has asked them to stop.
-Games have to be fun for everybody who is involved, or they're not acceptable. This means no teasing someone if it actually upsets them. Being mean to people or animals isn't allowed.
-No punishment for emotions. You're allowed to feel whatever you feel and say what you feel (though this is not a free pass for acting on those feelings). I try to empathize with them on their feelings and label their feelings- for example, "I know you're disappointed that you can't run in the kitchen". (That doesn't mean that I change the rule, but I do empathize with them not liking the rule)
-I try to keep the rules for kids to things that actually matter. I try not to have rules for my own convenience. I don't limit things like screen time unless it is causing a problem.
-You're allowed to cry (though yelling while crying is a different thing, and is not always allowed). Tears are involuntary, so aren't something to punish.
-Often tell the kids that I love them no matter what, that my love for them isn't contingent on achieving something or on their behavior.
-What's best for them is always more important than what other people might think or say, or what I feel. It's also not their job to keep me from feeling emotions.
-They breast-fed and co-slept when they were younger.
-I try to keep my expectations developmentally appropriate.
-Punishments can only be for things done voluntarily. That means no punishments for things like not being able to go to sleep or not doing well in school (though not lying quietly in your bed might be something I would punish). You might lose screen time for not doing well in school, but only if I think the problems in school are being made worse because of the screen time.
-I try to avoid "because I said so". I won't claim I always succeed.
-If I punish the kids, I generally give them warnings first (we do 1-2-3 Magic, so I "count" them), with the exception of physical violence, and always tell them what they did that was unacceptable.
-I stay away from trying to mold their interests or tastes, and I try not to make negative comments around them about their interests or tastes.
-I apologize to my kids if I realize that something I did or said was not right. If I yell, I apologize later, and say that I should not have done that.
-No scaring them, except as a game (and then only if they're not really scared). No saying things like, "Well, if you can't do this now, what are you going to do when you're in the next grade?" If they're scared of me, I would feel that I had failed in a big way as a parent.
I don't tolerate bullying, violence, or destruction of property from my kids, and this is because I am a gentle-ish parent. I do say "No" to the kids a lot.