After Dave left some comments about structural improvements to my out-building I felt I must try to address issues he had raised. Not sure if I understood everything correctly, but I hope so!!
I have built an internal frame around the door opening
The door I am going to use, is a sliding door that i was give, which I will fit on the outside of the building once I have nailed the outside panels on.
I could not obtain more 2″ x 5″ to strengthen the roof, but the local saw-mill did have a 2″ x 6″ left, so I have placed this mid-way under the rafters to provide support and help spread the weight.
I also found an old window which I have now mounted on one side of the building to provide a little light inside.
As usual, I am never alone when working ;>)