Designing shed studio 2.65m x 9m (hoping 2 storeys high)

Hi, reposting my original post under a more appropriate title!! (Thanks moderators for the corrections!). Ok, so I have been granted permission to convert the shed into a studio. I am based in London, United Kingdom. The measurements of the shed studio will now be 9m x 2.65m// The furthermost compartment is where the shed equipment will be (hose, lawn mower etc lol) The middle compartment will be the vocal booth, measuring about 1.5 x 2.4m. The front compartment will be the control room/ mixing room. I am also considering due to the small dimensions, to build a 2nd floor (to put a surround mixing/mastering studio, and a live/rehearsal room, to accomadate drum kit, and a piano (which can be used to record bands maybe?) I will be playing the music pretty loud by my eyes, but with my shed being in the middle of 3 other gardens, noise shouldnt be too much hassle. So a few questions, how thick will the outer walls need to be? Also, is it advisable to do a 2nd storey for a mastering room and live room? If so, how should the floor separate (to not effect the rooms below)? Absolutely any suggestions are appreciated, and any suggestions on my design at the moment. Thanks, Scott.