Well done PJ, this is indeed the Mini-powered, mid-engined Pearce Special, a technical college project begun by John Pearce for his degree work in 1970, and finally finished off and registered for the first time 13 years later in 1983. The pre-X1/9 targa-roof car uses a 1965 Mini Cooper S engine, and is still owned today by its creator John Pearce.
I will add some more photos of the car soon, but meantime, another point to PJ.