Born in Melbourn, Cambridgeshire, Hoy pursued a professional career as a chartered surveyor alongside his motorsport activities, working first for Bernard Thorpe and later for DTZ. He did not begin racing until his late twenties and graduated to international competition in 1985, taking on the full World Sportscar Championship that year, including the 24 Hours of Le Mans.
Through the late 1980s Hoy competed across a wide range of championships. His most notable result from this period was second overall in the 1988 All Japan Touring Car Championship. By 1991 he was ready to mount a serious BTCC campaign.
The 1991 BTCC was the first season run under Super Touring regulations. Hoy drove a BMW M3 entered by Vic Lee Motorsport. Although factory-backed entries from Vauxhall and Toyota were present, established BMW machinery was considered the benchmark, and Hoy made full use of his opportunity. He built a championship lead from early in the season that no rival was able to close, clinching the title in his BMW. He also won the Willhire 24 Hour at Snetterton that year, partnering Ray Bellm and Kurt Luby.
For 1992 Hoy was signed by the official Toyota team, running the Carina. He entered the final round of the season in a three-way title fight but was beaten to the championship by Tim Harvey's BMW. The Toyota proved less competitive in subsequent seasons; in 1993, during a round at Silverstone, Hoy was punted onto his roof by teammate Julian Bailey in an incident that prompted commentator Murray Walker to remark "the car upside down is a Toyota" — a play on the manufacturer's advertising slogan of the time.
In 1994 Hoy drove a factory-prepared Toyota Celica in the RAC Rally as part of the World Rally Championship, but crashed into a tree on stage four, though both he and his co-driver escaped unhurt.
Renault hired Hoy alongside Alain Menu for 1995. The early part of the season was plagued by mechanical failures, but he recovered to fourth in the standings with three late-season victories as the Renault Laguna became one of the fastest cars in the field. The arrival of Frank Biela's four-wheel-drive Audi for 1996 disrupted Renault's title ambitions, and Hoy slipped to ninth that year. He moved to a fading Ford programme for 1997 and 1998; 1998 produced his best results for some time, including a race win at Silverstone's Round 4 and a top-ten championship finish in an uncompetitive works car. Hoy raced independently for part of 1999 in an Arena Motorsport Renault Laguna, outperforming the other independents before entering semi-retirement. His last competitive appearance came at Silverstone in 2000 in a Vic Lee Racing Peugeot 306, where he took class pole for both races before retiring mechanically from each. In the 2002 BTCC season he worked as a television commentator alongside Ben Edwards and held a managerial role within the works Honda BTCC team.
Hoy's 1991 championship title — won in a privateer-entered BMW against growing manufacturer opposition — remains one of the more remarkable achievements of the Super Touring era. His ability to sustain a competitive career across two decades while maintaining a professional life outside racing, and his dignified conduct through illness, are remembered fondly by those who followed British touring car racing in its most commercially vibrant period. He is survived by his wife and three children.