As of 10 Oct 2018, I can't get my PowerApp to display currency in units of British Pounds (£) - I work at a company registered and resident in the United Kingdom.
I have attempted to format the data field's incoming value using the following value in the Textbox's Default Property.
Text(Parent.Default, "[$-en-GB] £#,###.##")
but this results in the amount being shown with a dollar sign at the front of the currency field. The SharePoint List shows the currency amount with expected British Pound prefix (£), but the view mode of the PowerApp only shows the field as a currency field with a Dollar Prefix.