Tried a new commute this morning, walking the mile or so to the nearest Boris Bike dock to ride in from there (going out for drinks after work). So much for the theory. It's one of the new ones, and according to a fellow frustrated person trying to get a bike out of it, the thing has been faulty for the last 2 weeks. 15 minutes and 2 phonecalls to customer services later I established the whole docking station was indeed on the blink, so another 5 minute walk to the next dock, which finally agreed to lend me one of its bikes.
The remaining journey was fine, traffic lights were kind to me (a good thing, those bikes weigh a tonne), the rain even held off. So despite the hassle it was still preferable to the crowded train/tube alternative!