I found a shed on Gumtree - it is pretty worn, but it was free and will be absolutely fine for now. It's a muted purple colour; not too unpleasant as it's tone is fairly grey. We 'uumm'ed and 'arrrh'ed about what to put the shed on slabs or pallets? Paving slabs would have required a gravel/sand/stone mix under and level ground. That would have meant bringing in heavy loads and fiddling about a lot.
Instead we opted to use the free pallets that were donated to our cause. The ground beneath was dug and roughly levelled by Papa; then a layer of membrane that will let the water through but keep any weeds down. Two pallets side by side then the shed on top.
We hilariously constructed it in a thunder storm! Desperately knocking it together and chucking on the roof just to get some shelter from the downpour! It may not be standing 'totally bubble' but we'll make it good tomorrow when it will be drier - we hope. I was so chuffed that I went back this evening to look at it and took this photo of the sunflower with our shed behind!