The earliest catalogue I have is the 1982  issue, in that it shows the 1st layout plan. it was called the Scenecraft Layout Plan. Designed by railway artist Eric Bottomley MGRA. There was also the metal frame to put the board on, it does not give the size but I assume it would be the same as the later Magnum II 5' x 2'6". I will try and get some scans uploaded later.
In regards to the track, GF had the sectional track made by ROCO in Austria as follows:
0080: 36" Y Super Liveway Point
0090: 13.5 degree Diamond Crossing
0060: 18" L/H Super Liveway Point
0070: 18" R/H Super Liveway Point
0032: Fixed Track Curve 480mm 15degrees
0031: Fixed Track Curve 261.8mm 30degrees
0021: Fixed Track Straight 104.2mm
0010: Yard length of Super Liveway Flexible Track.
I don't know if the points were ROCO or GF made, in the catalogue description it says "...you could enjoy the simplicity of fixed track, straight or curved, and with its own matching points - specially imported from ROCO of Austria, and some of the very few pieces of equipment we don't make ourselves."
It looks like it stayed like this till the Magnum II layout came out in '92-'94 when all track was gone from the catalogue and showing PECO Setrack on the train set boxes.

Thanks for that info, Taz.
Thinking about it, the only Magnum I like is either full of champagne or is a chocolate covered ice cream lolly

Wot? You can get them there, then?

Thought they were an Aussie invention