Hello Rob,
Reginald H. W. Cox's book "Military Badges of the British Empire 1914-18, 1st Edition, 1982", shows the same Interpreter badge that you have.
The badge is shown on page 245 in the United Kingdom of Great Britain and Ireland section under the heading Some Typical British Arm Badges.
Rob, I do believe the badge in the book is a match for your Interpreter badge
Cheers,
Invest