Hi Paul, these are British arm of service strips worn on the sleeve of the BD blouse.
Each arm of service used a different combination of colours. These are for the Pioneer Corps.
See here for more info:
Arm of Service Strips
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WW2 Australian Militia units as well as the 2/AIF wore colour patches so AMF (Australian Military Forces) and/or AIF would be a more accurate question.
All the best