Here's a pic of how I used to have my bike set up. You can see the U-Lock hooked through the rails of my Brooks B17. My cable lock is stashed in my oversized seat bag, along with my combo tool, spare tube, and patch kit. I applied a short piece of black electrical tape to each seat stay so that the U-Lock wouldn't chip the paint on the stays.
Since then I added a rear rack and panniers, so all of that stuff is stashed in one of the pannier bags.