The trickiest part of this set-up was in making sure I was using the right-sized hub for this bike. Knowing that there are usually just a couple different possibilities for rear-axle spacing in road and track bikes -- either 110, 120, 126, 130 or 135 mm width -- I carefully measured the spacing between the dropouts, then measured it again. The Raleigh came in at 126 mm so that's what I ordered. Hubs come in either 32 or 36 holes to accommodate the number of spokes on your wheel. I counted carefully too the spokes on the rim I planned to use -- 32 spokes, and so that is what I ordered. The one pictured above is black; I ordered mine in silver to match the front hub.
I ordered what's called a "flip-flop" hub, which has threading on both sides. That way you can put a freewheel sprocket on one side of the wheel (like I used to make the Raleigh a single-speed only) and a fixed gear cog (with no free-wheel action) on the other to run as a fixie. The advantage of that is that you have some options on how your bike is set-up. You can run it as a fixed gear bike all day, but if you're out on a longer ride and are getting tired or know that you'll be facing some big hills and simply want to be able to coast down them, you simply "flip-flop" the rear wheel, loosening the bolts, flipping the tire around so that the chain is on the freewheel cog instead of the fixed one.