I seem to remember there was an article in Air Enthusiast on the Sprite, a couple of issues before it ceased publication.
Probably the best account I have read on the aircraft.
Arthur Ord-Hume; "Butterfly from Essex",
Air Enthusiast, 131, September/October 2007, pp.22-25.
Amazingly when I tracked it down just now I found I already had a copy, bought for the next article along.
I have also just created a rather basic article on Wikipedia for
Essex Aero. I hope to add more about the Sprite when I get time - dimensions, estimated performance and stuff.
The Sprite and its Nuffield engine were a real tragedy. Back in in the early 1920s de Havilland designed the Moth but there was no suitable engine. He persuaded Frank Halford to develop what became the ADC Cirrus and the resulting Cirrus Moth created the Golden Age of aviation. After WWII a similar problem arose, as all the Cirrus and de Havilland Gipsy capacity was reserved for Miles and Auster's military contracts. Lord Nuffield, of Morris motor car fame, and Jack Cross of Essex Aero tried to pull the same trick again, with a Nuffield 100 hp flat-four and the Sprite. Sadly, when Nuffield was blocked from other markets by the monopoply-cartel tactics of Cirrus and DH, he bottled it and the Sprite died engineless.