Muffin,
This is why I ask everyone for quotes from the ANO.
The CAA, the BMAA and the AAIB all seem to want "differences" training - and it is a good idea (and not just because I am an instructor and need the students!) - but I can never find any mention in the ANO.
I suppose if you want to read the ANO cover-to-cover you can save yourself some cash!
As for differences, they are there - beware all who read this.
Yes, the C42 and the Eurostar are the identical airframe in microlight and light aircraft versions - so few differences there.
But try flying an X-Air, Thruster or AX for instance - then you'll see some differences.
And if you are used to Spam cans, then beware the lower inertia of the lighter aircraft - whether microlights or Gp A.
Safe flying all, it is not the paper that kills you,
XA