Thanks for that Aerohack. The Monaco "power egg" would have gone down well with today's PFA homebuilders particularly with a company designed cowling. Some of the designs at the PFA Rally do seem a little lacking on the aerodynamic front but what would I know, I'm a civil engineer not an aero engineer.
If all the designs had gone ahead there would have been a really good range of UK-built engines from 75 to 200 hp. Opportunity lost I guess.
Your reference to the Essex Aero Sprite was a new one on me. Do you have any further info?