To be short and sweet, I don’t see how bailing out the Bank of England in 1927 led to the Depression. That seems to be the Austrian explanation, in general, for the Depression from what I’ve read but I can’t make the connection.
The Economics of Legal Tender Laws (by Jörg Guido Hülsmann)
Advanced lecture on the origins of fiat money systems, explaining the transition from commodity money to commercial bank notes and deposits, and from there to fiat money.
He mentions a lot of history.
Perhaps you are thinking of bailout like a straight transfer of wealth, whereas the method adopted for propping up sterling (and for meeting other political ends) was inflation.