I retired this one a couple months ago after getting a proper Fixed/SS, but for the last two years I commuted through the winter on this: -
The frame was from an old Claud Butler Hybrid (hence the strange bar angle and short, steep stem trying to mitigate the longer top tube of the hybrid frame), it was lowered a bit later on), the chainset, bars, wheels and stem from my late Dawes Tourer, Brakes and levers 2nd hand from a cycling forum. Only new bits on the bike were the rack, chain tensioner and the single-speed conversion kit.
Unfortunately a lot of the components were old and worn out/rusted in place by the end so it wasn't really salvageable. I planned to turn it back into a 7sp flat bar and use it as a pub bike, but as I went to change components they had a habit of stripping or seizing so I gave up.