Wrote the context in the first paragraph, to explain what happened. Got questions in the end. Thank you!
So was in traffic in kings cross, London. I spotted a BMW 5 series estate which was parked on the side of the road facing the main road. My gut instinct was that it is a undercover police car. Drove past them and then they joined the road. They then went through the bus lane (not allowed it's a 24/7 bus lane, but they're police so it's fine) and switched lanes to go behind me. After about 30 seconds they switched on the blue lights and gave me a toot of the siren. I went into the bus lane and pulled over. They went behind me so I knew it's for me. Officer got out and told me my windscreen tint is illegal and I could potentially recieve a fine and 3 points. I decided to play dumb in an effort to get a bit of sympathy and get away with it basically. I told them that the tint man told me its legal. He said unfortunately he sold me down the river. This wasted time. Then a lorry wanted to leave a building site and was getting annoyed cos we were blocking the exit. So the police told me to go on my way and take off the tint ASAP.
Could I get in trouble for this traffic stop, can i recieve a letter? They gave me no paperwork. Will it stay on their systems so if I get pulled over again the officer will know that I was pulled over on the 4th February for illegally tinted windscreen? Also if I was stopped again, could I avoid a fine and points by taking off the tint at the roadside?