RAF or AM Acronyms

I am reading a 1950’s RAF document at the moment and a couple of acronyms have come up that I have not been able to “decode”. These acronyms are associated with stores or military equipment procurement.

A.D.E – located in the USA during WW2
D.D.E – Think it is an engineering position in the Air Ministry
D.M.T – Director of Motor transport?
P.S.C.O – Assocated with maintenance units or equipment sections

Any help or ideas as to what these acronyms stand for would be most welcome.