In 1974, Derek Cook entered four rounds of the Southern OrgansBritish Formula Atlantic, driving a Chevron B27-Hart/Ford, and finished twentieth overall, without scoring a point. For 1975, he entered a round of the BARC F3 Championship, but did not compete, whilst he entered eight rounds of the Southern Organs British Formula Atlantic, and nine rounds of the John Player British Formula Atlantic, using both a Chevron B27, and a March 75B-Ford during the season. He moved into the Shellsport International Series for 1976, completing three races in the Chevron, whilst he also competed in three races of the Indylantic Championship with that car, without scoring any points in either competition. For 1977, he entered a single round of the European Formula Two Championship, and six races of the Shellsport International Series, taking eighth place overall in the latter championship, with 22 points, in what proved to be his last competitive season of racing. His solitary F2 race was at the Daily ExpressInternational Trophy, held at Silverstone Circuit, where he finished 11th in the Chevron, of 12 finishers.
Dealership
In 1988, Cook formed his DC Cook chain of dealers. In 1996, the franchise made a turnover of £180 million, with pre-tax profits of £5 million – with the capital return being 2.77%, a figure well above the industry average. Following this record profit, the company set about expanding, with the aim of increasing turnover to £400 million. This, however, would prove unsuccessful; although turnover had increased to £337 million by 1999, an internet venture between DC Cook and Totalise Eurekar came at a point when the main portion of the dealership were beginning to enter difficulties, and in 2000, the share price had fallen to 9p, with shares being suspended. The company then entered receivership in 2001, with debts totaling £27 million, with receivers stating "after rapid expansion the dealer failed to bed down its new acquisitions. The rationalisation of the past two years did not work and the company collapsed under a debt burden of £27m". Following the collapse of DC Cook, the Cook family started DC Cook Direct, which sold discounted new cars. However, a year prior to his death, this company also encountered difficulties; following complaints by customers, South YorkshireTrading Standards Service cancelled the company's membership of a fair business scheme. In 2008, DC Cook Direct entered liquidation, with the company being run by his daughter, Paula. In addition to the formation of DC Cook Direct, Derek Cook had also formed Motor Solutions in 2002, an online discount dealer of new and used cars, which was later sold to Virgin Group, and renamed as Virgin Cars, before its closure in January 2006, seven months after Cook's death.
On 1 May 2005, Derek Cook, and his wife Winnie Cook, were out driving during a holiday in Monaco, when they were involved in a crash. Derek Cook was killed in the crash, whilst his wife escaped with injuries. Following his death, his daughter, Paula, took over the DC Cook Direct dealership franchise, and controlled it until its collapse at the end of 2008/beginning of 2009.