correct- RAF used 'English' miles upto Sept '45 when they converted to Nautical miles (knots), involving the change of every asi
AFAIK headings were usually given as 'vectors' in degrees (10 deg increments)
I THINK this was magnetic.
(there was a second format using 'bearing' and iirc this used the other North, however i may be mixing the 2 up)
need to find reference to this