The "Abbreviate" option should be able to format to either thousands, millions or billions for the whole visualisation.
Because it only rounds to the nearest thousand, million or billion depending on what the value is, you end up with confusing summaries in tables, like the below. As you can see, a user scanning this will get confused very quickly because the third column, first row should really read "£0.3m" rather than "£334k".
There should either be an option at the global visualisation level or an option to specify the rounding.