Thanks for that, youv'e answered my question very well, it seems a logistical nightmare.
C studs found on ebay for £2 each compared to B&Q@ £14 each and they only have 1 lol, the £2 ones have to be collected from a distance of approx 80 miles, ie hire a van (maybe)this seem common at the mmoment.
Unbelievably B&Q have 3x2 at £5 if it can be delivered,who knows.This maybe what I decide on, speed of completion is of the essence as my son needs to be in there, it's very complicated, he has health issues.
C stud is suposed to be better for less sound transmission as you prob know, but,,,
I have used timber (on a garage wall) but not metal, not sure how easy it is to work with.
Basically just going to build a cavity wall 14ft x 8ft internal dim with the outer shell not touching the inner, supposedly, (uncoupled?) this will be posistioned somewhere in the 7m x 7m wooden shed after I have weather proofed it, sadly on removal of the wall linings all the base timbers are done for as is a lot of the cladding which is hidden behind asbestos, it has an asbestos roof to make matters worse, but that is staying, at upto £100 a mtr removal cost,ie 3 to £5000. It's going to be a bodge ( I will not have any help what so ever as we have just relocated miles away from freinds and family and James can't help (complicated))just to make it last a while, he/we may move to something more suitable in the futre.
We will have to keep an eye on damp and ventilaton.