Direct Query Regional Settings

Using Direct Query to an MDX model and custom visuals e.g Bullet Charts (both Microsoft and OKViz variations tested), the currency fields formatted for British Pounds (£) all become dollars ($). The standard power BI visuals all show £s for the same measures as expected.

I have tested the same situation when using import mode with none of these issues present.

I presume this is related to the "Regional Setting" option in Power BI Desktop however this is not available when using Direct Query. 

Any ideas? 

It makes the custom visuals a bit useless for British businesses with this scenario.

(I am using the latest version of Power BI Desktop optimised for Report Server [March 2018])