If your thinking of the ones up top the park, there's zero run-in. I used to skate that park all the time. Best bet for lazy urban is the Banting stairs that people skate at. Use the first ten for a run-in to the second handrail. I've seen kickers on the 20-odd set near the 10/12 sets too, usually a little past the light pole.
I know some snowboarders who've set things up at the forks. But really, if the barracks is all you can think of, you really need to get around London more.