With very few exceptions, almost all British sports cars manufactured in the postwar era have 12V electrical systems, including those from Austin-Healey, Jaguar, MG and Triumph.
Some models, such as the Austin-Healey 100, Austin-Healey 100-Six, MGA, MGB and MGC utilize twin 6V batteries that are wired together to deliver their voltage, but these are still 12V systems.