Bits and pieces off my On-One singlespeed bike:
On-One Twelfty seatpost - 27.2 x 350mm length £6
On-One Inbred stem 80mm 6 degree rise standard clamp £10
On-One Inbred saddle £10
On-One Mary bars - £15
Shimano Deore disk brakes M535 (I think) a few years old but work well. New pads. Can include 160mm rotors if required. £25
If anyone wants more details or photos then reply on here and I'll sort something out.
Greg