Steven,
Until recently I hadn't realised how many changes in Dress & Embellishments the various British Army Medical Services had undertaken since 1908, especially QAIMNS who never seemed satisfied with their uniforms. I can see it being a fascinating area to research, so best of luck.
If you are ever in the UK, the AMS museum at Mytchett is excellant. The curator is both knowledgable and approachable.
http://www.ams-museum.org.uk/museum/
Stephen.