Actually there is no legal requirement for differences training, and certainly no need for a signature in the logbook. All you need is familiarisation training. Legally you could just climb in and go but as microlights are quite different then a little instruction is essential. As it is a single engine piston aeroplane it is covered by your SEP Class rating.
Absolutely right (Whopity usually is
).
Perhaps worth adding though that hours in a microlight will NOT count towards the hours required to revalidate an SEP (land) class rating on the basis of experience.