(1) use the old Hornby kit seen here with a coat of paint, replacing the floor and adding some dirt.
Funny you should say that,its exactly what I've been doing over the weekend! I have also turned it into a single road shed with a bit of measuring and careful cutting. Once the filler is dry and I get the time it will be repainted internally and clad with Wills sheets and detailed to give me something a bit different.