If you search on "Sunderland" in the photo search section at
www.airliners.net you'll find loads more photographs of those two Sunderlands in service.
I haen't seen a photo of the low pass at Heathrow, but one of the volumes of John T. Evans' series, "Sunderland, the Flying Boat Queen" shows the 'boat doing a low pass down the runway at Gatwick.