There is a simple explanation as to why, though.
January 2018 wasn't a great month for car sales. In the US, overall deliveries fell by one percent compared to the previous year, while over in the UK sales were down by 25 percent according to a report by Top Gear, with SUVs representing the only segment that saw growth. By far the worst performing manufacturer, however, was Chevrolet, which sold just one car in the UK last month. And by that we literally mean a single car. Yikes. Still, it's an improvement over the year before – in January 2017, Chevrolet sold a grand total of zero cars in Europe.
There is, however, a simple explanation to this shortfall. As of 2016, General Motors removed Chevrolet's mainstream offerings in Europe and the UK to better distinguish Opel and Vauxhall. Consequently, only the 2018 C7 Corvette available as a Stingray, Grand Sport and Z06 variants, and the 2018 Camaro are sold in the UK. They're not even sold officially either, as dealers are having to legally import them, but they're not converted to right-hand drive models. It isn't known which model represents the only car sold in the UK last month, but it can only either be a 2018 Camaro or Corvette which are rare sights across Europe.
Alternatively, it's possible that Chevrolet may have had some vehicles left on stock back from when it was selling rebadged Opel cars. According to data from CarSalesBase via Motor1, Chevrolet sold two cars in Europe in December 2017, one in November, and not a single car in October last year. Its best-selling year in Europe was way back in 2005 with 211,737 deliveries. It's a better story in the US despite a slight decrease from 2016, as Chevrolet shifted more than two million vehicles in 2017 and has so far sold 141,947 in January 2018.