your summary seems correct to me. Boths sheds are securely fastened to the ground. The sheds have a 6 inch gap between them. I realise the cable would need to be protected. My questions would really be:
How should the cable be protected?
How do I run the cables, in terms of connections etc in existing shed?
How should the cable be protected?
How do I run the cables, in terms of connections etc in existing shed?