Worth noting, that people do get stopped and questioned, for reasons other than Schengen.
Certainly, my understanding is that since Brexit, UK police are no longer able to access the SIS database. Shortly before Brexit happened, they were doing an exercise, to remove details of UK citizens from SIS.
But it is quite possible that some were missed and there is no way of knowing for sure, if your details are still on there, without asking the PPU. They could presumably find out for you.