Possibly filmed when ABBA were in London for the premiere of "ABBA - The Movie" ie. when they were on Blue Peter and had those famous Dorchester Hotel balcony pictures taken - Agnetha was wearing a brown wrap over her jeans in those pictures and she wears it here also.
As the advert is for
the UK Epic version (blue cover) then it figures that it was filmed in
London. And it's possible it could have been directed by Lasse
Hallström as he would have been in London for the première also.
Thanks to Richard Knight