I guess you're looking for the name Quest? But this is not Quest, this is the Straker's car.
I think some clarifying is in order, here you go: For the 1968 Gerry Anderson's movie "Doppelganger" three cars styled by Derek Meddings were constructed by Alan Mann (the man responsible for Chitty-Chitty Bang-Bang). They were based on Ford Zephyr's running gear and fitted with 1,6-litre Cortina engines.
After seeing the cars on the film set, one Sidney Carlton, together with a friend named David Lowes, established the Explorer Motor Company to buy brand new Zephyrs and clothe them in a glassfibre body imitating the movie cars. The resulting car was named Quest and offered for 3000 pounds (to compare: at that time Daimler Sovereign costed 2360 pounds, a 3-litre Ford Capri 1290 and Jaguar E-Type 2160). Unsurprisingly, no orders were ever received and the company folded in 1970.
Also in 1970, the Doppelganger cars were bought by Pinewood Studios to be featured in the new series UFO. One car (brown) was driven by SHADO (Supreme Headquarters Alien Defence Organisation) Commander Straker, another (silver) by his deputy Colonel Foster. I don't know anything about the third car being used in the series. BTW, all of the cars still exist, but are in a very derelict condition. Here's a still from the UFO series showing both cars together, the Foster's car in 1999, a comparison of both cars (the silver one was longer and had different air scoops) and a photo of the Quest (probably the only ever constructed). I've had somewhere pics of the Straker's car current condition but can't find it now.