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As you say, fit is important. I'm a UK 9-10 street size and I'm a 41.5 in la Sportiva, but 44 in Unparallel and anywhere in-between in other brands.
Something like the Katana is an easy fitting shoe good for most stuff. I think Otakis are a great all-round shoe with a good balance of performance and fit.
For me 5-10 is a no go because they kill my achilles and they're too narrow.
Look at la Sportivas comparison chart for a good understanding of what you might want to look for: Chart
UK 9-10ish.