Dan spotted this item on ebay for us, a bamboo fixie from Masulli. Definitely a one-off. The bike’s a spot on match for my size but not my wallet.
The Masulli Bikes website has more info on their amazing products.
Note, the bamboo fixie shown in the picture isn’t the one selling on ebay. This one’s from Bike Radar.
See also this article about more bamboo and wooden bikes.