It wasn't registered as a Ginetta, that's for sure. As I said it is something of a mystery to me. I got this picture from the son of the chap in the photo who was the car's second owner for a time in the mid-late '60s. He isn't sure of it's provenance but it's assumed to be a totally home built effort.
I personally don't really see too much similarity with the G3/ Fairlite, the grille opening on this car is much higher up and of a completely different shape, though it is very unusual that it is only one registration number away from that car pictured, however TPK is (I believe) a Surrey registration and Ginetta cars were based in Suffolk in 1961, so it's unlikely that car was an ex-works car. Like I said, a bit of a mystery!