i've got more than several boots from that period, barry, but none of them include anything from meddle other than OoTD and Echoes.  in the 'live at pompeii' video, there's a modified version of Seamus, but it's not really even that; just blues acoustic guitar (waters), harmonica (gilmour), and howling dog (wright's); no vocal.  never ...

it is, without question, roger waters who is speaking at the beginning of 'us and them.'