HK and I visited a friend who has had a Burrows 'expensive Raleigh 20' (called a 1D perhaps) with carbon chaincase/ chainstay and drum brakes for quite a while. A lovely bit of kit but the single speed is quite limiting. A Pinion gearcase would be heavy but very nice.
Tony also showed me an ex-Dutch national team motorpace bike with an enormous drilled Campag ring and a beautiful chrome Carlton with headclip headset, Airlite hubs, Chater-Lea cranks and inch pitch block chain. The Carlton is just about my size and I'd love to take it around a proper velodrome at speed, after gluing on a couple of reliable tyres!