Being someone that wears a kilt every day, and also the sgian duhb, I've found the 99.9% of English police are well aware of the law. I've been asked to let a few look at it, and its been promptly returned after them having had a look. The only time I'm asked to surrender it is when I'm entering a secure area, eg Courts, Scottish Parliament, Houses of Parliament and the like. In all cases it's been returned to me as I'm leaving.
The only thing to remember, if you are carrying a live blade and become engaged in an altercation it can be claimed you made a threat with the weapon, at that point without very good evidence to the contrary, it's likely to be taken from you. And that is based on an incident where somebody collieded with my car, while we were arguing who was wrong the other person started getting aggressive, I took my sgian duhb and locked it in my glove box before facing him down. He saw what I had done and called the police to say I threatened him with a knife. Fortunately for me, 3 people had observed the incident. When the police arrived I admitted I had a sgian dhub, I said as the guy was getting aggressive I had locked it away in the locking glove box and also locked the car so I could not possibly be involved in any violence while carrying a bladed weapon. The police were ready to confiscate the sgian duhb when the witnesses stepped in and confirmed what I had said. The idiot eventually admitted that I had not threatened him and had locked the knife away because he was getting aggressive towards me. (As a side note, his insurance company didn't argue the case and paid out in full saying that as he had made a false claim to the police under caution, they couldn't believe his version of the accident, and if it went to court he would have lost.)
I also have the relevant web page saved to my mobile phone, and a small laminated card with the specific law quoted on it just in case I meet some officer who does not know the relevant passage (3 in over 20 years)