As an aside, Reliant also used the SS1 chassis for the MGF prototype - the V8 RWD PR2. The PR1 was M16 FWD by Motor Panels of Nuneaton, the PR3 was the K series FWD by ADC of Luton (that Austin Rover eventually proceeded with), the PR4 was a steel PR2 (never built) and the PR5 was a design excercise on a TVR chassis.
Reliant were the only ones to deliver a fully working prototype in the 27 weeks given by Austin Rover.