I'm assuming that since according to ITN the crew were advised of the separation of the cowls from the engines by ATC (seen by the CT) immediately after rotation, the natural option would be to return to LHR immediately, which presumably would have been agreed with ATC if no other problems were apparent that would otherwise have necessitated diversion to LTN or STN.
So, I see no issue with returning to LHR.
Of course, if it had not made it, then you can imagine what would have followed in the media. Thank heavens all were safe and sound.