I hope it is true, but don't hold out much hope, since the source is the Daily Star. They could have learned from the post pinned to the top of the Support Justice for Rolf Harris Facebook page that he'd been using that PI for the past four years. The rest could be invention.
I don't understand why they're calling that woman a victim either, since he wasn't convicted of her allegations. She was also quoted recently by the Mirror over the story of him being on school premises (
source).
The tweeting of his name in that way was grossly prejudicial, IMO. A fishing expedition dropping hints that genuine victims of crime wouldn't need.