Thing is, Harry probably was hacked. Plenty of people around him were, so he likely also was.
But he's thick as pig shit, so he's gone on the stand and blabbered about how sad the stories made him instead. He's also somehow managed to pick a load of stories that were printed by other outlets first, so the Mirror has a completely reasonable explanation of 'we lifted the story from other outlets'. He's pissed off the judge by not turning up day 1, he's tried to flip questions onto the silk cross examining him, and then sounded like a conspiracy theorist by saying that even if the Mirror lifted the story from somewhere else they'd also have had to hack him to get more info that they then didn't bother to publish.
He's got an enemy as blatantly vile as the tabloid press, they probably did do what he's accused them of, and yet he's got the rare talent to thoroughly balls it up by playing billy big bollocks, waltzing onto the stand unprepared, and thinking a Diana mention would win everyone over. Absolute idiot.