Ian Gilroy was in After Hours with Geoff Chunn and Neil Finn in 1976. In 1977, punk-theatrical group the Plague (organised by Richard Von Sturmer) recruited a band from Westlake Boys High in Auckland for musical accompaniment, namely Tim Mahon, Mark Bell, Andrew McLennan and Ian Gilroy. The Plague played with the Scavengers and at the Nambassa Festival in January 1979, later splitting up and the four musicians forming the Whizz Kids, who toured NZ extensively and released a single. Ian left to join the Crocodiles and was replaced on drums by Don McGlashan (the Whizz Kids minus McLennan would change their name to Blam Blam Blam). Ian ("Killjoy") headed to Melbourne to join the Swingers in December 1980. He remained in the band till their 1982 split.
Much thanks to Carolyn Bedwell for the information from:
The Mechanics of Popular Music, A New Zealand Perspective (Mike and Jeremy Chunn)
Blam Blam Blam biography (Kiwi Rock web site)
Blam Blam Blam (Propeller Records page)
For more check the Swingers biography.