The puppet people of Toobworld assume all of the qualities of the shell that they are inhabiting. So when a spirit wore the shell of Margaret Thatcher, it became for all intents and purposes the Iron Lady hersellf:
As far as her flesh-and-blood appearance in Earth Prime-Time, - is she represented by Lindsay Duncan, Sylvia Sims, or Andrea Riseborough? - Mrs. Thatcher definitely can count on 'Are You Being Served?' in the episode "Monkey Business". All that was seen of her was her arm as she shook hands with Mr. Humphries.