After ten years with Jaguar, the first five as an indentured commercial apprentice, and a subsequent two years with British Leyland as supplies manager of its bus division, in January 1972 Barrie joined Reliant Motor Company as supplies manager and was appointed to the board in February 1974. He led the development of purchasing, material control and parts departments, and the sourcing of the Robin; Otosan Anadol estate (Turkey); Scimitar GTE SE5a, SE6 and SE6a models; Kitten car, estate and van range; TW9 pick-up; and Helicak taxi for Indonesia. He was appointed director of product development and supply in 1976, then deputy managing director a year later, and headed product strategy from 1976-8, which included a replacement for Anadol designed by Bertone (FW11). Barrie worked with sales director, Roger Musgrave and former Jaguar chairman, FRW ‘Lofty’ England, to develop a pan-European sales network for Scimitar and Kitten ranges. He resigned in February 1978, following the rejected management buyout attempt led by managing director Ray Wiggin, linked to high-profile auto industry businessmen, Johannes Eerdmans (ex-Jaguar USA), John Barber (former MD of BL), Donald Healey MBE and Tony Good (former director of Jensen); and the subsequent JF Nash takeover of 1977.
In October 1978, he became director of supplies of DeLorean in Northern Ireland, before being appointed chief executive during the 1982 receivership. He then led Sir Clive Sinclair's electric vehicle venture, before assisting Proton of Malaysia; Yulon Motors of Taiwan; the Iranian national car company Iran Khodro; the Ministry of Industry of Indonesia; the Department of Trade & Industry of UK; the European Union; SMMT; and many other automotive projects across Europe, Asia and North America. He led the manufacturing launch co-ordination of the Lotus Elan (M100) from 1986-88; the negotiation of an EEC grant for Rover Group in 1992; and a cost reduction programme for the Lamborghini Diablo through 1993. When MG Rover entered administration in 2005, Barrie developed the Project Kimber business plan and led an all-British bid to acquire the MG-related assets from the administrators, having negotiated the transfer of the rights to the discontinued smart roadster from DaimlerChrysler. Following the administrators' acceptance of the competitive offer from China’s Nanjing Automotive, having then secured the rights to the AC brand, he developed a new business plan focussing on the smart roadster. This collapsed in the wake of the global financial crisis of 2007/8. In his subsequent retirement, Barrie has written his first book, John Z, the DeLorean & Me - tales of an insider, published in 2015.