It stinks that you had to be put in that position but I applaud you for taking steps to protect yourself as well as the neighborhood you live in.
It’s such a shame that your cat had to pay the price. I’d be pretty bent out of shape too.
I don’t know what the laws are like in the UK but hopefully when they seize the dog, they’ll give the owner a new set of bracelets and a ride to the station.
I think you did the right thing.