We have a separate garage at the end of our garden that can hold 3 cars. The previous owners did a bit of motor racing so the thing is soundproofed already, apart from the door. I currently have my setup in there but we're still pondering over what to do about the door (5 meters wide!) The cheapest option would be to use a timber/plasterboard option (£600 i think), however the wife would prefer double glazed upvc patio doors (£3k cheapest quote!) to retain the garden view. What degree of soundproofing would this provide?