O-D -not often I can get one over on you!!
You and the OP are both correct in a way.
Warburton was also awarded a
USA DFC, so he had 2 x DSOs, 3 x UK DFCs and 1 x DFC from the cousins.
Total 6!!
[Edited to add:]
Details of his service and the awards are
here.
And he was killed 4 weeks after his 26th birthday!!