Home base for the project was initially behind the butchery and the bodywork had to be winched down from the first floor to complete the build. A pear tree was then sacrificed to get the finished car out the yard and onto the road. Autocar tested the first unit in May 1960 and reports were positive. Cottrell ordered the second car, which like the third and fourth units, was built behind the butcher shop.
With these cars making use of mostly Austin A35 mechanicals, it was originally planned that Gilbern GTs would be sold as basic body and chassis kits with buyers then sourcing their own running gear. With this opening the doors up to some below-par workmanship and part selection, the decision was quickly changed to see the cars supplied with all-new parts in component form. With the body painted, wired and trimmed all an owner had to do was fit the engine, gearbox, back axle, wheels, exhaust system and minor trim bits. A job that was said to be possible in a weekend and even better, it meant that the owner could avoid the purchase tax of between 45% and 49% levelled at complete cars.
With space fast becoming an issue, in 1961 Smith borrowed money from his father, bought what was the old Red Ash Colliery and dumped a bunch of second-hand prefabricated buildings on the site. A few of these units became the Gilbern factory, while the majority were rented out to other businesses to help the cashflow. With half a dozen employees working, including the hands-on Smith and Friese, the production rate measured in at a single unit per month. Powertrains evolved with the times, moving from the popular A-series and Coventry-Climax options to MGA 1600cc (The Motor magazine tested one in 1961, recording a top speed of 94.3mph (151.8km/h) and 0-60mph (97 km/h) in 13.8 seconds) and then to MGB 1800cc – in this guise the vehicle became the Gilbern GT1800.
Staff complement increased to 20 and production ramped up to a car a week. The American market was considered, with a trio of left-hand drive examples going stateside, but real focus was on local consumption.