Shed ventilation

[slopey]

Hi all:

One last question regarding my shed revamp. After much discussion and thought, and much appreciated advice on this site, I have decided to insulate my 9m x6m corrugated steel shed with Ametalin 'Silver Sark XR' and then line the internal walls with Formply and the roof with plywood.

I have attached some photos (not of great quality) which I hope will explain my predicament. Where the gable roof comes down to the rear wall, there is a gap of about 200mm from the roof, horizontally, to the wall. I am thinking this was done to allow ventilation in warmer weather, and reduce condensation. As I am going to line the roof and walls, what would be the best method to close in that gap? I am trying to keep my costs down so employing a builder to fix it is out of the question. My other problem is that the back wall of the shed is on the boundary of my neighbours yard, so I only have access from inside the shed.

All suggestions will be greatly appreciated.

Thanks

Slopey.