We just did an 8 night stay at the Park Tower - pleasant room with modern decorations. Good size bath with both tub & shower stall. Located next to Harvey Nichols and near Harrods, very upscale shopping area. There is some construction on the 1st floor, but I don't think it should bother you.
As SPG Gold, didn't get any upgrade or breakfasts even after asking. I guess getting the highest "basic" floor is what they consider a preferred room.