i've been nosying at these free plans - thanks for doing all the legwork & putting them on here for free btw

Question is, I can understand that a pretty good weight saving will be made by building insulated sides instead of the solid 3/4 ply ones in the plan - but from an insulation point of view does it make a huge difference comfort wise?
Here in the UK we have quite a large difference in temperature through the year - I just wondered whether taking the easy route to building would result in condensation pouring down the walls in colder weather or unbearably hot temps in summer

Cheers,
Swizz...