Obviously once you accept some composites, it has the potential to undermine the 'geographical accuracy' approach. But not necessarily: it may indeed explain why, not only do hills and island appear to have moved around to make Ransome's world, they also appear to have changed form: like the island they are not one place but several, and that can be as true for houses, views and people as it can for islands. And perhaps, if 'a part' of the island is where it seems to be on the map, perhaps 'parts' of the other places are too.
Take Stephen Spurrier's original map of the lake, and compare with a contemporary Ordnance Survey map:
Also looking at the maps, my childhood-suggested-Beckfoot - Belle Grange - seems to be in around the right place. There are so many suggested Beckfoots, and I have no knowledge of a Ransome connection to the house. But it is certainly worth considering.
I shall return to Belle Grange for a future article. I shall leave this one here for now - but there is more to follow! Please comment widely!