So sorry to read this Kazz.
My mum killed one on the road last year and she was absolutely devestated for weeks. It never had a tag on it's collar so at least you have the closure of knowing you did the right thing by owning up and being able to return the wee thing to it's owners. My mum's ex (long since dumped, he was a horrid man at times) drove out, picked it up and put it in a bin on the side of the street!

He had no empathy at all. 'Don't worry, it's just a cat' was his attitude to the whole situation. I put an add in the paper and the newsagents in the lost and found, but was never contacted.
I wish that when I lost Nipper, the person would have had the decency to do as you have Kazz, but they just left her on the side of the road for all to see, upset a lot of the locals before I was even informed. Had to collect her myself, not something i'll ever get over but would have made it so much easier to cope with if the person had told me when it happened at least. I'd have known at least that she died instantly and wasn't left suffering. It was very kind of you to wrap him up and take him over to them, that will have helped a lot for sure. Must have been very hard for you but well done.
R.I.P Oliver. x
Hope you are ok Kazz. x