I just had a look at my old Mandrakes and discovered that some of them are actually Australian. Most have pre-decimal prices so I think they are from the 1960s. Most of them also have covers by Keith Chatto. Stll not sure when the run started or finished though?
Come to think of it I do have a few australian mandrakes. at home, including some pre-decimal ones... here is the Australian portion of my Mandrake collection for those who are interested:
-- Super Comic Series (Australia) --
No. 16 ('Mandrake Discovers the City of Gold')
-- Consolidated Press (Australia) --
 No. 02 (On The Stage, The Missing Pearls, Norvell's Revenge, In Hollywood, Mystery Of The Two Faces)
-- Gordon and Gotch (Australia) --
No. 15 ()
No. 28 ()
No. 29 ()
No. 33 ()
No. 37 ()
--Mandrake The Magician Album Edition (Australia) --
(Magicians Never Tell, Deadly Cobra, The Crystal Cube)
-- Budget Books (Australia) --
 No. 1 Master of Illusion ('Spellbound', 'Lothar's Afternoon' )
 No. 2 Spellbinding ('Might Magic', 'Masters of Disguise')
-- FREW (Australia) --
I'm missing the dates on most of them, but from memory (I'm not near my collection right now), the G&G comics are from the 1960s.. The Super Comic Series was earlier, I think (again, from memory).
But as for FREW mandrakes prior to 1990... no idea.