Barry, like the idea - I was thinking of something on the same lines. I have a very large filing cabinet that I might use for the power tools, and I was thnking of installing it inside a strong wooden cabinet, and anchoring it the floor, the hand-tools will be probably be also locked away in some form of lockable cabinet.. plenty to think about!!
Ok, so after speaking to the woodman, i'm going to go for some joins on the shiplap, but in such a way that it's staggerd, so looks like part of the design, this has helped me reduce the wastage considerably, and the cladding has come out £110 cheaper than my first calculations, and there's a high chance it might get delivered on tuesday, so all hands to the pumps!!