I remember reading about that, and the Jaguar one. The Ford one was developed by Orbital. I don't remember anything about it being made of plastic. It used crank-case induction, with roller big-end bearings to minimise the amount of oil needed in the mix. There was some sort of valve in the exhaust that adjusted itself with revs to keep it in tune, so the torque curve in the test cars was very good. IIRC it was 1.2 litre and developed 90bhp.
All I read about Jaguar's was that it would be a 3.6 supercharged (I guess in place of crank-case induction) V6 and was intended to replace the V12. Looks like the supercharged 4-stroke V8 filled that role nicely instead.
Is that the "Cathedral" that Robbie Coltrane danced to?