File the widened ‘polarization tip’ off the one prong of the plug so it’ll plug into the old 220 V. British (round prong) tip adaptor. Use the brown extension cord not only to bring the electric closer to you (in rooms that only have 1 plug for the whole room), but also to multiply the plug so you can charge your devices along with those of your roommate. :-) Many rooms will have only one plug.
Great idea. My preference is the Monster Outlets to Go (http://amzn.to/14vmRdP) which is super compact and incredibly useful. I never travel without mine. The cord is not as long as what Doug has shown above, but I like the design. There is also a version that includes a couple of USB charging ports in place of one or two of the standard 3-prog outlets. Highly recommended.