Diziet's Studio Build - garage

I was hoping someone on this forum could be kind enough to help with a question about the foundation for my soon to be built studio? My question is where to put the thermal insulation (polyurethan or polysstyrene) in relation to the isolated foundation structure. I've posted to possibilities below. The idea with the insulation under the slab was the architects. My concern with this is that the thermal insulation will not perform well acoustically and pass vibrations directly through to the outer found (the inner found is essentially resting on the outer found with the thermal insulation seperating). The garage will be built from scratch and won't really be a garage at all excpt that I'm trying to design it so that any future buyers of the house could easilt turn it into one if needed. The inner room will be concrete (100mm) walls with a concrete beam and block roof. The outer will be concrete (140mm) walls with a pitched roof of standard construction but with isolation added between the beams. Both inner and outer will be structurally seperate and air tight (apart from ventilation via big silencers). The inner foundation will be isolated from the outer.