I remember when Samantha, one of our black cats, went missing when we moved house. I drove all round the local roads to see if she had been hurt. She was always a roamer and we eventually suspected that someone had taken her in, but it was the not knowing which hurt the most.
I have just been reading up about newts. They are apparently fine where there are places near water for them to hide - low shrubbery, log piles and so on. Birds and grass snakes are their worst predators as can some cats, but if the cats are not worrying them they will be fine. One thing I did learn is that the Great Crested Newt is protected by
law and you are supposed to inform people if you have one. I think I would be tempted to just let things carry on as they had been.