My wife bought herself a Carlsson in the summer. Being four wheel drive and an automatic will probably make it thirstier than the manual front wheel drive version, but after hearing stories of doom, the fuel consumption is not too bad.
Normal very short journeys around town show about 16 mpg. Average is around 24 mpg and a run to Newcastle and back in the summer was around 30mpg. Better than that on the return, we went north via the rural roads of Lincolnshire.
Overall not much different from my Hirsched 9-5 Aero.