What counts as "vastly" expensive? In every single other respect, the Sony Xperia Z5 Compact looks perfect for you. Indeed, it's on my own shortlist right this second.
It's 127×65×8.9mm, so very much the same size as what you have. Android. Best-in-class camera. I imagine it's no better or worse than any other Android phone for file transfer. Available unlocked. Sony is better than most at upgrades. But it's £300.
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It's 127×65×8.9mm, so very much the same size as what you have. Android. Best-in-class camera. I imagine it's no better or worse than any other Android phone for file transfer. Available unlocked. Sony is better than most at upgrades. But it's £300.