"Mr Guy Fawkes ranks alongside Russell Morris' The Real Thing as the highwater mark of Australian pop production in the late '60s, a phenomenal single from a most memorable band." (Glenn A. Baker, liner notes to So You Wanna Be A Rock'n'Roll Star? Festival Records, 1998)
To cut a very long story ridiculously short, the first Dave Miller Set was a renamed line-up of Dave Miller And The Byrds that moved to Australia from New Zealand in 1967. Soon after, the band broke up and Dave Miller re-formed the Dave Miller Set with lead guitarist John Robinson.
For the full story, see the detailed history of Dave Miller at Milesago, as well as the (NZ) Byrds and Dave Miller Set pages at Bruce Sergent's NZ Music site. Both sources tell Dave Miller's story in the wider context of the New Zealand and Australian music scenes of the day.
See also Dave Miller's interview with Steve Kernohan, in which he tells of splicing a lo-fi tape of the original version down to shorten it before presenting it to the band.
See Seasons Of Change by Blackfeather which originated in a Dave Miller Set live performance.
From 1969 album Sunrise, produced by Jimi Hendrix.
Eire Apparent was formed by four former Irish showband musicians who met in the UK. Initially named People, they were renamed when they were taken up by Jimi Hendrix's management and signed to his record label.
Eire Apparent toured England with Hendrix and then America, when founding member Henry McCullough quit, to be replaced by Mick Cox, writer of Mr Guy Fawkes.
McCullough is now better remembered for his membership of Joe Cocker's Grease Band (he played on With A Little Help From My Friends) and the first line-up of Paul McCartney's Wings.
References: All Music Guide entries on Eire Apparent, Henry McCullough and Wings.
Further reading: Bruce Eder's detailed Eire Apparent article at AMG which also outlines the later careers of the band members.