Blunt nose with no badges doesn't give much away. It's registered in 1981
Construction is basic and base is a Metro, as the wheels show. But it's not a one-off
UPDATE 31 MAY 2011: I received an e-mail message of Richard who believes this car to be the prototype of a car named 'Roamer' built by a man named George Davies of Birmingham. Apparantly the car is indeed based on the Mini Metro and has a steel frame of 50 x 50 x 1.6 mm tubes that's been clothed with steel too. I couldn't find any more on the Roamer or Davies, so the question remains: who knows (even) more?
UPDATE 28 August 2012: A similar car is to be auctioned in the US. Click here