The gentleman in question was Bill (?) Bonner and the Chippie was G-ARWB. Saw it at Farnborough in probably '78 or '80 and also at Shoreham. Think there was also an article about it in Air Pictorial around then. Seem to recall the name "Sapphire" connected with it and was under the impression that it was based on the Ford Granada engine, though may well be wrong. The Chippie is still around and is Gispy powered once more.
Remember reading about the gas-turbine Auster at Fairoaks, and also Viv Bellamy and his mates at Eastleigh sticking one in a Currie Wot!