Allner began his managerial career with AP Leamington. He led AP Leamington to the Southern League Premier Division in 1983. However, Leamington were denied promotion to the Football Conference, their place being taken instead by the club that had finished second that year, Kidderminster Harriers. Soon after this, Allner left Leamington and took charge at the Worcestershire club. Kidderminster quickly established themselves as a top non-league side under Allner's management, winning the FA Trophy in 1987 and reaching the final in 1991 and 1995, in addition to making the final of the Welsh Cup in 1986 and 1989. Their most successful season came in 1994–95 when they reached the fifth round of the FA Cup, knocking out second-tier side Birmingham City (Allner's first club as a player), and Preston North End. They also won the Conference title that season, but were denied promotion because their Aggborough ground was not deemed up to Football League standards.