Got it!
It's New Zealander Ferris de Joux's de Joux Special, AKA "Ferraguar".
I could see those BMC Farina rear lights so figured that if it wasn't the UK it just had to be Australia or New Zealand (NZ as it turns out)...
The Ferrari started out life as a 4.1/2 litre F1 racing car in the early 1950's, being raced by Taruffi and Froilan Gonzalez amongst others. It arrived in New Zealand in 1955 and took part in the New Zealand Grand Prix in 1957, after which the engine was used to power a speedboat. Ferris de Joux bought the chassis and spent two and a half years building the de Joux Special out of it, but decided on a 3.4 litre Jaguar engine as he thought that more suited to the character of the car. The body was made out of glassfibre by de Joux himself, and he actually called it a Jaguar-Ferrari, reputedly hating the name "Ferraguar"! He used the Pininfarina 250GT as inspiration for the shape and many parts from production vehicles were used, like the Austin A40 rear lights and rear bumper.
Apparently it took de Joux 2500 hours of work to complete this car!
Unfortunately the de Joux Special no longer exists. The chassis has been used to recreate the original Formula 1 Ferrari and is in the collection of one Bernie Ecclestone..